Neither is flexible, nor strives for completion. They are both implementations that try to map the ActivityPub vocabulary on an existing web-application domain.
They are not ActivityPub servers, but web-apps that use the ActivityPub vocabulary to federate, which is what I meant in the grandparent post when I mentioned the classic mistake of ActivityPub implementers. :D
Try Honk[1] or GotoSocial[2]?
[1] https://humungus.tedunangst.com/r/honk [2] https://github.com/superseriousbusiness/gotosocial