Discord came around after I had already gone FOSS as much as possible, so I've never actually used it. I host two Matrix (Synapse) servers, one for friends and family and one for work. I don't use it for large public chats, just friends or work, so my largest rooms are 10ish people each. The server side of things has never given me a problem, I easily run it on a 1 vCPU VM with 3 GBs of memory (I'm sure I could give it less if I needed to).

On the client side, Element works well enough, but I do wish it felt a bit further along after all of these years. Calls work reliably if one end is a computer (so computer to computer or computer to phone), but phone to phone calls are a complete roll of the dice if they will work properly. Notifications are a complete mess. I have Element open on my desktop right now with zero notifications, if I turn on my laptop and open Element (same exact account) it will show a handful of rooms with notifications until I go mark those as all read. The worst is when you get a call that isn't actually a call but a stuck notification from somebody that called you days ago.

I mean I do love it, there is no alternative for me. I simply don't even think about Discord or other proprietary apps as even a choice. I hope open source, decentralized software keeps gaining momentum and the rough edges are touched up a bit.