Does generic ActivityPub node software exist?

Ah, I see.
Yes, that is exactly the idea of the Client To Server part of ActivityPub.
You have a standardized REST API so that a variety of diverse clients can use 1 server.
It is the chapter 6 in the spec.
Please note:
The acronym community often refers to this as C2S :slight_smile:

This is misleading to many new developers because some big players invented their own REST API …
We had a session at ActivityPub Conf before pleroma added C2S :

and there is a category


btw: A list of all supporting servers might be useful …