I just recognized that dozens of fields in our target environment do have an unmanaged layer, even when we only import managed solutions into this environment. (At least I thought so.)
These are Calculated Fields, Rollup Fields and some Global Option Set Fields.
I couldn't remove the Active Layer from these fields and after researching I found this
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/developer/calculated-rollup-attributes?view=op-9-1#additional-limitations (refers to OnPrem)
experience.dynamics.com/.../
and this interesting post:
https://www.philcole.org/post/calculated-fields-and-managed-solutions/
So my assumption is
1) Calculated Fields always end up in unmanaged layer in target systems.
2) Updating Calculated Fields always requires "Overwrite Customizations" when importing Managed Solutions OR manually updating them in target environment.
Is there anybody out there who can confirm these two assumptions?
If you have any "best practices" how you handle Calculated Fields in your projects with Managed Solutions I'd be happy to get some more advice here.