if youre talking about activitypub federation, does it matter what software you use? theres a reason its a standard protocol.
i would hope that any instance of any federating software would just pick up where it left off with regards to activitypub.. cept your server will be throwing a lot of 'content not found'.
now, other pleroma or derivatives might be speaking with your instance over some custom api, and that obviously wouldnt work.. but so?