My last expirence with XMPP is very dated, my old groups in EvE online used it and it was perfect for its role as a sort of internet pager to summon the horde of nerds. Im aware there are many new related projects, discounting it seems a bit premature now, if you have any recomendations I would love to read their docs.
My concern is that I would have to pitch what ever project we landed on to a semi-technical group of gamers with a handful of admins to run things. (Trying to avoid a platform that gen-z would complain about, and they already roll their eyes at me when I mention spaceships and spreadsheets).
Note for Obsidian, there is a git plugin that can auto-push/pull from a repo. I put my repo on a server and have multiple devices use it as a sync feature (there is also a VPN to my home network involved). Not sure how well it works on the android app (its pure lazyness as to why I haven’t tried that yet…)