I signed up with the main matrix.org server years ago to try it out. I like to play with the the various clients every couple months to see what new features have been implemented. The element developers just released element x which looks nice.
praxis
I am not aware of any good solar punk wiki projects. There are however several other great wiki projects online that we can link and and contribute to. Here are a few wiki projects related to the environment, sustainability, and various diy technologies
Appropedia.org - The sustainability wiki
On the topic of high quality information of the commons, I think what we really need is a decentralized federated wiki technology, like lemmy but for wikis. One that uses some combination of consensus based peer review, version control, and author accreditation. As far as I know, nothing like this even remotely exists - yet.
Edit 01 - Added Hacker | Solar! There are some good articles, not alot of activity in the past year
Edit 02 - I just saw the post talking about the official slrpnk.net wiki! Great work folks!
Interesting, I was not aware of the metadata issues with matrix. I hope that's something they can solve soon.
I have to say I haven't done much research into XMPP. I'll probably dabble with XMPP at some point when I get the time. I've been waiting for both projects to mature more before diving in too deep.
I'm really interested in a real time communication technology that combines the decentralized peer-to-peer and privacy features of briar with the speed and polished UI of telegram.
I read at some point that the matrix developers want to develop the matrix protocol to work peer-to-peer without a central homeserver. If that is the case then matrix may be headed down that path.