Matrix would be a much better choice IMO.
Turns out FB is capricious and has no problem pulling the rug out from under those companies and the communities they foster on Facebook without notice or recourse. Pages and groups with hundreds of thousands of followers can be wiped off FB and there's nothing your business can do about it.
If I were in their shoes, I'd just use FB as a funnel to an online property that I own and control.
It's worse in every way. It's not even close to something as polished as Discord.
1. "Open in browser" is a good start, but then the registration process is downright painful. Discord doesn't require you to register at all to try it out, just to pick a nickname, it's vastly better for onboarding.
2. Requires unique nicknames. A chat app with unique nicks? this has to be a joke right?
3. As usual with FOSS, the worst part is the UI/UX. The whole design is extremely confusing. At first glance it appears the app only supports 'rooms'. But it seems that there are 'communities' and 'spaces' too? I have no idea what's going on. Discord just has servers with channels and private messages and it's all clearly indicated in the UI.
Listen, I do want to use open and free alternatives if possible. But let's be realistic and stop pretending that something like Matrix is anywhere near Discord. A more reasonable alternative would be Zulip.