*** UPDATED 11 June 2021 *** Version 2
NOTE: PLEASE USE A TEST ENVIRONMENT FIRST AND TAKE NOTE OF THE STEPS. These are just 5 simple steps to manually enable a different version of XRM SDK that would skip URL validation through Regional Discovery Service and fall back to Global Discover Service.
PRE-REQUISITE:
You must have installed .NET 4.6.2 or a later .NET Framework version before moving forward with the following
LINK Download Microsoft .NET Framework 4.6.2 (programma di installazione offline) per Windows 7 SP1, Windows 8.1, Windows 10, Windows 10 November Update, Windows Server 2008 R2 SP1, Windows Server 2012 e Windows Server 2012 R2 from Official Microsoft Download Center
Below one of the typical errors that you might receive when deploying the new CRM SDK without installing .NET 4.6.2
(1) Download the CRM SDK package (it will download a nupkg file): Microsoft.CrmSdk.CoreTools
https://www.nuget.org/packages/Microsoft.CrmSdk.CoreTools/9.0.2.11
IMPORTANT: When you have downloaded nupkg file be sure to UNBLOCK it

(2) Rename the file extension to .zip and unzip the file to a folder. The files we’re interested in are the dlls in content\bin\coretools folder.
(3) Stop NST
(4) Pull
Microsoft.Crm.Sdk.Proxy.dll
Microsoft.Xrm.Sdk.Deployment.dll
Microsoft.Xrm.Sdk.dll
Microsoft.Xrm.Tooling.Connector.dll
and copy them over the older versions in the NST folder (make a backup of the older versions of these DLLs of course) and also RTC folder (needed only in dev clients to run New-NAVCRMTable runs and finsql.exe compilations where these assemblies are referenced)
NST folders:
C:\Program Files\Microsoft Dynamics 365 Business Central\<version>\Service\DataSources\XrmV9
C:\Program Files\Microsoft Dynamics NAV<version>\Service
Client folders:
C:\Program Files (x86)\Microsoft Dynamics 365 Business Central\<version>\RoleTailored Client
C:\Program Files (x86)\Microsoft Dynamics NAV\<version>\RoleTailored Client
NOTE: Pulling or replacing the DLL files in the Windows Client folder is only needed to run the New-NavCRTable cmdlet and/or to compile objects within CSIDE. This is typically done by developers using test workstations or workstations dedicated to develop code. These steps are not necessary to be done on end users workstations.
(5) In the following 3 config files
C:\Program Files\Microsoft Dynamics NAV\<version>\Service\Microsoft.Dynamics.Nav.Server.exe.config
C:\Program Files (x86)\Microsoft Dynamics NAV\<version>\RoleTailored Client\Microsoft.Dynamics.Nav.Client.exe.config
C:\Program Files (x86)\Microsoft Dynamics NAV\<version>\RoleTailored Client\Finsql.exe.config
add or change the following to the assemblyBindings:
<dependentAssembly>
<assemblyIdentity name="Microsoft.Xrm.Sdk" publicKeyToken="31bf3856ad364e35"/>
<bindingRedirect oldVersion="0.0.0.0-9.0.0.0" newVersion="9.0.0.0"/>
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.Xrm.Tooling.Connector" publicKeyToken="31bf3856ad364e35"/>
<bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0"/>
</dependentAssembly>
NOTE: Changing client side config files in RTC folder (Microsoft.Dynamics.Nav.Client.exe.config and finsql.exe.config) is only needed to run the New-NavCRTable cmdlet and/or to compile objects within CSIDE. This is typically done by developers using test workstations or workstations dedicated to develop code. These steps are not necessary to be done on end users workstations.
(6) Restart NST
(7) These 2 object may fail to load or compile because they are looking for different SDK version, then open TAB5330.TXT and COD5330.TXT in designer and change explicit references to .NET CRM Assemblies version 8 to be completely without a version like e.g. in Release notes for NAV 2018
https://docs.microsoft.com/en-us/dynamics-nav/d365-sales-modifications-for-upgrade?branch=crm-technical-upgrade
Change:
DotNet "'Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.<class/type>"
To:
DotNet "'Microsoft.Xrm.Sdk'.<class/type>”
Change:
DotNet 'Microsoft.Xrm.Tooling.Connector, Version=2.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.<class/type>”
To:
DotNet "'Microsoft.Xrm.Tooling.Connector'.<class/type>”
Save and successfully compile TAB5330.TXT and COD5330.TXT
NOTE: This step MAY not be required with version 13.x or 14.x or higher since these versions comes with TAB5330 and COD5330 with assemblies already declared without version
NOTE: You must have a valid development license to perform this task
(8) Run the client and test connection once again. It should be successful.