I’d recommend Matrix. It’s not perfect, but I dislike the alternatives more. Btw if you decide to give it a try, don’t use matrix.org, it’s too large of an instance which makes it slow and kind of ruins the decentralization aspect of it. tchncs.de seems like a good choice. I’d also love to give anyone in need of a matrix server a registration token, though registrations are not open on gregtech.eu, so contact me for a key if you’d like.