What are the Discord Alternatives?
There are many and it's hard to know what's good and whatnot with the discord alternatives. What is or isn't good and what is or isn't complete? There are many I'll talk about today along with the pros and cons of all of them.
The list
Revolt/Stoat
Honestly if you can look past its many issues it is a rather competent discord alternative, though with time it has been slowly getting worse rather than better. Overall it can be a decent choice if you're not looking to self host it, if you wish to self host it you'll need to rebuild all of the clients to point to your new instance.
Harmony
Harmony is still in development but is improving with time. It strives to be discord compatible, though this does not mean you can contact people on discord on harmony, it just means existing discord bots/clients can often be modified trivially to use harmony rather than discord assuming harmony properly supports the API.
Spacebar
Spacebar has poor management issues, and has undergone many poor changes. I can no longer recommend its usage, as it has had many problems with time. Despite this it still is somewhat discord API compatible
Polyphony
It really sounds like the dream, a FOSS, federated discord alternative with Discord API support. Though at this point there's nothing more to say than that. There is some work being done on the project, though nothing to really see as it's not complete enough for that, and it's trying to avoid the pitfalls of Matrix by thinking about the spec before actually implementing it, which this does have many advantages, it does mean that this project is a lot slower moving. I don't know if this project will ever be finished.
Matrix
I have a lot to say about Matrix, though I'll keep it short. It is not a discord alternative. It lacks the ease of use of discord and has a lot more focus on channels rather than guilds. (or "spaces" as matrix wants to call them) And of being on there its been a poor experience of the classic matrix things you hear about on the internet, "Message can't be decrypted", the invites to very illegal rooms, the poor instance level moderation. I don't know what to say other than treat it more like a telegram alternative.
Fluxer
No. Just no. It uses AI, and is not currently FOSS, with the most up to date source code being behind a paywall. They also have serious maintainability issues. Just don't use it.
TeamSpeak
It's proprietary and has much more of a focus on voice channels than guilds and I'd personally say it's not a discord alternative either. I don't have much more to say about this.
Have I Forgotten Anything?
If I have please open an issue here, though keep in mind I have other stuff to do as well, so I might not get to it immediately.