It’s also made to be decentralized. Seems voice chat works already. Screenshare and video chat don’t seem to be released yet, but I was told that if you host your own instance, you can turn them on (vidchat and screenshare are probably still in beta/are experimental features I assume). UI layout is comparable to Discord.
Me and a friend are considering installing an instance on the server our peertube instance is installed on.
Matrix is an interoperability protocol (like activityPub, which mastodon, friendica, Lemmy, pixelfed etc… all use to communicate with one another) rather than the actual application being used.
The UI you’re describing is probably Element, which is the most common matrix implementation used, though others do exist. A good example is probably rocket.chat; they’ve leaned harder into the discord like feel, whilst making use of the matrix protocol.
As for Stoat chat; It’s a rebrand of revolt chat, who have previously resisted calls for federation due to the perceived complexity of implementing (or creating their own i guess) protocol. That’s not to say it doesn’t have it’s uses; but it would be silly to assume people won’t try to steer you towards federated services on the fediverse 😉 and stoat don’t seem to have changed their stance on the matter.