I've seen quite a couple of attempts at copying Discord's UI over to other services like IRC, Matrix and XMPP, and indeed making entirely new protocols like Fluxer.
Discord's quality isn't in the UI, it's the UX. Slack has an almost identical UI to Discord, but is a remarkably awful service that is clunky and hard to use. Trying to copy Discord's UI isn't going to get you anywhere, and you hazard reinventing Slack (ew).
They key is get right all the tiny things Discord nailed. It needs to be performant, it needs to have great customization features, it needs to support all the structuring features with text channels, threads, forums, etc. It needs to look polished, choice of colors, icons, font, button placement, all of it matters. Setting up a group chat or a server should be trivial. Discord assembled all these features and streamlined them. That's what makes it so good.
