I tried a different Admin user, - getting the same error.
On D365 instance, I tried to create an Entity which I intended to form part of a solution and got this error:

And the details below. I don't know what other permissions I need to grant! Thanks.
Unhandled exception:
Exception type: System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]
Message: System.Exception: EntityService.Create failed for entity ObjectTypeCode: 10273 LogicalName: new_junk caught exception: Microsoft.Crm.CrmSecurityException: Principal user (Id=2d1d5e08-8f37-4d04-8a94-458c8537c74c, type=8, roleCount=1, privilegeCount=558, accessMode=1(Setup/Stub user with filtered privileges from associated roles. Consider changing user AccessMode to Full (without privilege filtering)), is missing prvCreateCustomControlDefaultConfig privilege (Id=481f2478-dcd7-4145-9aec-ab1e789ccdc9) on OTC=9755. context.Caller=2d1d5e08-8f37-4d04-8a94-458c8537c74c
at Microsoft.Crm.BusinessEntities.SecurityLibrary.ThrowCrmSecurityException(SecurityPrincipal principal, Guid privilegeId, Int32 errorCode, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityLibrary.CheckPrivilege(Guid user, Guid privilege, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandlerEntityPrivilegeCheck(Object sender, SecurityTraits traits, SecurityAttributes attributes, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateSecurityCheck(Object sender, ExtensionEventArgs e, BusinessEntity entity)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandler(ExtensionEventArgs e, Object sender)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.PreCreateEventHandler.Invoke(Object sender, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.<>c__DisplayClass173_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.ObjectModel.CustomControlDefaultConfigService.Create(IBusinessEntity entity, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass107_0.<CreateUIData>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute(ILogger logger, EventId eventId, ActivityType activityType, Action action, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute(ILogger logger, XrmTelemetryActivityType activityType, Action action)
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.TryCreateUIData(EntityCreateInfo entityInfo, ExecutionContext context, Boolean IsInternalSolutionContext, Boolean isPostCoreEntityCreate)
at Microsoft.Crm.Metadata.EntityService.CreateInternal(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass22_1.<CreateInternalHelper>b__3()
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context) ---> Microsoft.Crm.CrmSecurityException: Principal user (Id=2d1d5e08-8f37-4d04-8a94-458c8537c74c, type=8, roleCount=1, privilegeCount=558, accessMode=1(Setup/Stub user with filtered privileges from associated roles. Consider changing user AccessMode to Full (without privilege filtering)), is missing prvCreateCustomControlDefaultConfig privilege (Id=481f2478-dcd7-4145-9aec-ab1e789ccdc9) on OTC=9755. context.Caller=2d1d5e08-8f37-4d04-8a94-458c8537c74c
at Microsoft.Crm.BusinessEntities.SecurityLibrary.ThrowCrmSecurityException(SecurityPrincipal principal, Guid privilegeId, Int32 errorCode, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityLibrary.CheckPrivilege(Guid user, Guid privilege, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandlerEntityPrivilegeCheck(Object sender, SecurityTraits traits, SecurityAttributes attributes, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateSecurityCheck(Object sender, ExtensionEventArgs e, BusinessEntity entity)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandler(ExtensionEventArgs e, Object sender)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.PreCreateEventHandler.Invoke(Object sender, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.<>c__DisplayClass173_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.ObjectModel.CustomControlDefaultConfigService.Create(IBusinessEntity entity, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass107_0.<CreateUIData>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute(ILogger logger, EventId eventId, ActivityType activityType, Action action, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute(ILogger logger, XrmTelemetryActivityType activityType, Action action)
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.TryCreateUIData(EntityCreateInfo entityInfo, ExecutionContext context, Boolean IsInternalSolutionContext, Boolean isPostCoreEntityCreate)
at Microsoft.Crm.Metadata.EntityService.CreateInternal(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass22_1.<CreateInternalHelper>b__3()
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
--- End of inner exception stack trace ---
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass20_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.Metadata.EntityService.Create(EntityCreateInfo entityInfo, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass17_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.Metadata.EntityService.Create(EntityCreateInfo entityInfo, Guid solutionId)
at Microsoft.Crm.Application.WebServices.SystemCustomization.EntityCreate.Execute(Guid solutionId, ParameterBag paramBag)
at Microsoft.Crm.Application.WebServices.SystemCustomization.SystemCustomization.CreateEntity(XmlNode data): Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #CEC7E7FCDetail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ActivityId>e8c3ac07-9af6-4e12-ae4c-3cf66eb2bc88</ActivityId>
<ErrorCode>-2147220970</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>System.Exception: EntityService.Create failed for entity ObjectTypeCode: 10273 LogicalName: new_junk caught exception: Microsoft.Crm.CrmSecurityException: Principal user (Id=2d1d5e08-8f37-4d04-8a94-458c8537c74c, type=8, roleCount=1, privilegeCount=558, accessMode=1(Setup/Stub user with filtered privileges from associated roles. Consider changing user AccessMode to Full (without privilege filtering)), is missing prvCreateCustomControlDefaultConfig privilege (Id=481f2478-dcd7-4145-9aec-ab1e789ccdc9) on OTC=9755. context.Caller=2d1d5e08-8f37-4d04-8a94-458c8537c74c
at Microsoft.Crm.BusinessEntities.SecurityLibrary.ThrowCrmSecurityException(SecurityPrincipal principal, Guid privilegeId, Int32 errorCode, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityLibrary.CheckPrivilege(Guid user, Guid privilege, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandlerEntityPrivilegeCheck(Object sender, SecurityTraits traits, SecurityAttributes attributes, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateSecurityCheck(Object sender, ExtensionEventArgs e, BusinessEntity entity)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandler(ExtensionEventArgs e, Object sender)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.PreCreateEventHandler.Invoke(Object sender, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.<>c__DisplayClass173_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.ObjectModel.CustomControlDefaultConfigService.Create(IBusinessEntity entity, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass107_0.<CreateUIData>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute(ILogger logger, EventId eventId, ActivityType activityType, Action action, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute(ILogger logger, XrmTelemetryActivityType activityType, Action action)
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.TryCreateUIData(EntityCreateInfo entityInfo, ExecutionContext context, Boolean IsInternalSolutionContext, Boolean isPostCoreEntityCreate)
at Microsoft.Crm.Metadata.EntityService.CreateInternal(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass22_1.<CreateInternalHelper>b__3()
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context) ---> Microsoft.Crm.CrmSecurityException: Principal user (Id=2d1d5e08-8f37-4d04-8a94-458c8537c74c, type=8, roleCount=1, privilegeCount=558, accessMode=1(Setup/Stub user with filtered privileges from associated roles. Consider changing user AccessMode to Full (without privilege filtering)), is missing prvCreateCustomControlDefaultConfig privilege (Id=481f2478-dcd7-4145-9aec-ab1e789ccdc9) on OTC=9755. context.Caller=2d1d5e08-8f37-4d04-8a94-458c8537c74c
at Microsoft.Crm.BusinessEntities.SecurityLibrary.ThrowCrmSecurityException(SecurityPrincipal principal, Guid privilegeId, Int32 errorCode, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityLibrary.CheckPrivilege(Guid user, Guid privilege, ExecutionContext context)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandlerEntityPrivilegeCheck(Object sender, SecurityTraits traits, SecurityAttributes attributes, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateSecurityCheck(Object sender, ExtensionEventArgs e, BusinessEntity entity)
at Microsoft.Crm.BusinessEntities.SecurityExtension.PreCreateHandler(ExtensionEventArgs e, Object sender)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.PreCreateEventHandler.Invoke(Object sender, ExtensionEventArgs e)
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.<>c__DisplayClass173_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.ObjectModel.CustomControlDefaultConfigService.Create(IBusinessEntity entity, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass107_0.<CreateUIData>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute(ILogger logger, EventId eventId, ActivityType activityType, Action action, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute(ILogger logger, XrmTelemetryActivityType activityType, Action action)
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.TryCreateUIData(EntityCreateInfo entityInfo, ExecutionContext context, Boolean IsInternalSolutionContext, Boolean isPostCoreEntityCreate)
at Microsoft.Crm.Metadata.EntityService.CreateInternal(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass22_1.<CreateInternalHelper>b__3()
at Microsoft.Crm.Metadata.SqlTelemetryHelper.LogSqlTimes(Action action, String operationName)
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
--- End of inner exception stack trace ---
at Microsoft.Crm.Metadata.EntityService.CreateInternalHelper(EntityCreateInfo entityInfo, MetadataHelper metadataHelper, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass20_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.Metadata.EntityService.Create(EntityCreateInfo entityInfo, ExecutionContext context)
at Microsoft.Crm.Metadata.EntityService.<>c__DisplayClass17_0.<Create>b__0()
at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)
at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)
at Microsoft.Crm.Metadata.EntityService.Create(EntityCreateInfo entityInfo, Guid solutionId)
at Microsoft.Crm.Application.WebServices.SystemCustomization.EntityCreate.Execute(Guid solutionId, ParameterBag paramBag)
at Microsoft.Crm.Application.WebServices.SystemCustomization.SystemCustomization.CreateEntity(XmlNode data): Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #CEC7E7FC</Message>
<Timestamp>2019-06-20T09:48:27.0179193Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault>
<ActivityId>e8c3ac07-9af6-4e12-ae4c-3cf66eb2bc88</ActivityId>
<ErrorCode>-2147220960</ErrorCode>
<ErrorDetails xmlns:d3p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>Principal user (Id=2d1d5e08-8f37-4d04-8a94-458c8537c74c, type=8, roleCount=1, privilegeCount=558, accessMode=1(Setup/Stub user with filtered privileges from associated roles. Consider changing user AccessMode to Full (without privilege filtering)), is missing prvCreateCustomControlDefaultConfig privilege (Id=481f2478-dcd7-4145-9aec-ab1e789ccdc9) on OTC=9755. context.Caller=2d1d5e08-8f37-4d04-8a94-458c8537c74c</Message>
<Timestamp>2019-06-20T09:48:27.0179193Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault i:nil="true" />
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</InnerFault>
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</OrganizationServiceFault>