The breaking change would be to:

• Obsolete public Func<Type, bool> TypeHasTags; replace it with:

  public virtual bool TypeHasTags(
  #if NET
      [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembers(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)]
  #endif
      Type type)

• Obsolete public Func<Type, IEnumerable<string>, bool> TypeHasMatchingTags; replace it with:

  public virtual bool TypeHasMatchingTags(
  #if NET
      [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembers(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)]
  #endif
      Type type,
      IEnumerable<string> tagsToMatch)

I agree, this is a significant breaking change, as this is probably one of the more frequently customized classes in FluentMigrator. We can publish a version of FM in 8.x.y version that marks these as obsolete and adds the above replacement interfaces, so that people have a transition clue. Then we would merge this PR to create FM 9.0.0 release.

Originally posted by @jzabroski in #2252 (comment)