To me it looks like the features are about 80% there, can't find the screen sharing, login with QR doesn't exist. Not really sure how to even search for some features because the naming is so extremely bad. "matrix automation" "element bot". E.g. this is a very poor collection: https://element.io/integrations Looks like custom emotes are still missing.
But let's say all of that exists and works.
What other features are essential for an opensource community that only discord provides?
I think we're talking about different things then. I don't need something for an opensource community. I need something for ALL communities I'm a part of. Because I'm already in 40 of them and 5 of them are FOSS projects. So switching those over increases friction, if it's not a total replacement.
As for forums, they are for async. Are you going to seriously tell me discord is a good forum replacement?
This is inverted. I don't need to defend why the platform I'm on is good, (it's not), you need to explain why forums are supposed to be better (they are significantly worse).
Documentation belongs on a dedicated website, Issues belong on some gitlab or something instance. If I have a question, I want the answer reasonably quickly or I'm just not going to use the software you're providing. If I'm nice, I'll leave a post on the bug tracker that the install/getting started documentation didn't work.
Forums serve no purpose anymore.
Right now, I'm going to stop using element/matrix again for the forseeable future because there are no communities with public rooms I'm interested in.