As far as I can see everything works like before and my tests succeeded.

Some code changes were reviewed by me (not 13k) and look fine. Please test jobs after deployment.

Generaly speaking as c# inheritance is limited to a single base-type it is not advisable to mandatory enforce inheritance from a framework type. Instead interfaces should be used.
In respect to EF using concrete entity-types and dbcontext base class defines hardcoded table-names that cannot be adjusted by the framework-using code. It implies an application cannot have more than a single process/process-step table within a given db-schema. In addition to that it also disallows to define any other custom base-class for the dbcontext.
Instead the framework should define interfaces to be implemented by the concrete entities (Process, ProcessStep and ProcessStepStatus) and those interfaces should be used within the framework code.
Concrete Entity-classes implementing those interfaces and dbcontext base class may still be provided (in a separate implementation package) but the use of those should be optional.