See this page for a list of all the third party protocol support https://pidgin.im/plugins/?publisher=all&query=&type=Protoco...
The Matrix protocol itself sometimes also leaves much to be desired. It's much more modern than XMPP, that's true, but the fact that you can't send an image with text in a single message is just... How did everyone involved decide that it's reasonable? Did people design the UX on top of a protocol when it should always be done the other way around?
The main issue I'm having with every single of the modern IM apps is that they combine the chat list and the chat switcher into a single control. It's part of the overall unfortunate trend of touchscreen-ification of desktop UIs. Tabbed chat windows need to make a comeback, yesterday.
We're not really moving forward with the proprietary chat protocols (Slack, Teams, Whatsapp). It is a much, much harder problem to solve than MSN and Yahoo ever was.