Groups are not (yet) supported by the proposed interoperability anyways… and don’t hold your breath. It will likely take years for Meta and the EU in courts before they stop with their malicious compliance.
There are working WA bridges for XMPP and Matrix though if you are willing to selfhost.
I think once groups land in Pixelfed and the new app is released on the official app-stores, which will hopefully both happen this month, it is probably the best option if people are used to IG and Facebook.
Personally I think Solarpunk building illustrations should clearly show the utility for community infrastructure (mixed use, local recycling etc.) and exhibit features that improve disaster resilience.
Hmm, I find some of the questions and assumptions a bit odd. Like are there really a significant number of transhumanist anarchists? At most I have seen some “anarcho-capitalist” leaning transhumanists that like the former have very little in common with actual anarchists.
Edit: ah, I remember reading some anarcho-transhumanist zine a while ago, which was not so bad (mostly about space exploration), but it seemed like total fringe and not in any way popular amongst anarchists at all.