I will no longer be able to assist with development nor debugging actual issues with the software... Quite juvenile behavior from the devs. It stemmed from this issue where the devs continuously argued in public by opening and closing an issue. Anyway, thought I would keep y'all apprised of the situation, since these are the people maintaining the software you are currently using.
They don't have to be incompatible.
Yup.
In fact, you don't need to be based on Lemmy's codebase in order to be compatible with Lemmy. See: Kbin/Mbin, https://azorius.net, https://narwhal.city (which seems to be lotide's flagship?), or heck, Mastodon (although the interoperability UX there isn't the best)
Building on Lemmy would make things significantly easier, especially regarding the quirks of Lemmy's implementation of ActivityPub & FEP-1b12 though, so a fork would be the path of least resistance.
The fedi has a long history of forks for a variety of reasons. Hell, Misskey alone has like a bajillion forks to the point where it's a meme how many of them there are, and yet they're all compatible.
Of all the misplaced priorities by the dev team I really think this is one of the biggest. If they just fixed authorized fetch Lemmy would almost certainly be the goto host for groups among the broader Fediverse.