Replace DefaultIdType GUID with ULID?

[tpmccrary]

I am trying to replace using System.Guid to using a ULID (either https://github.com/Cysharp/Ulid or https://github.com/RobThree/NUlid)

I found this issue, #172, that was merged. Apparently, it allows for multiple key types, however, changing the DefaultIdType to System.Ulid in Directory.Build.props causes errors:

/home/user/misc/test-api-boilerplate/src/Core/Domain/Common/Contracts/BaseEntity.cs(8,36): error CS0029: Cannot implicitly convert type 'System.Guid' to 'System.Ulid' [/home/user/misc/test-api-boilerplate/src/Core/Domain/Domain.csproj]

Guid seems to be very imbedded into the system, so it is making me doubt this is even possible.
Anyone have a solution?