I find this first hand experience interesting. It is however difficult for me to figure out if the difficulty they had was due to an intrinsic complexity of ActivityPub (which the article suggests) or an attempt to use ActivityPub in a context where it was not a good fit.
https://inqlab.net/2021-11-12-openengiadina-from-activitypub-to-xmpp.html
Using ActivityPub is considerably harder than we expected:
- Using JSON-LD as an RDF serialization is very complicated. It requires the usage of algorithms (e.g. the Expansion Algorithm or the Framing Algorithm) that are incomprehensible and just pure madness. JSON-LD maybe was really just not intended to be an RDF serialization and trying to use it as such is painful.
- There are practically no implementations of the ActivityPub Client-to-Server protocol (C2S). This made developing and testing the client and server more time-consuming as we had to develop the protocol in lockstep on client and server. At the end we were still only compatible with our own software.
- ActivityPub is not a complete specification and many additional protocols need to be implemented (e.g. WebFinger) in specific ways in order to be compatible with existing servers.