I've personally not had terribly good experiences with Matrix. I found it to be slow at times, but more annoyingly, it would very consistently not un-encrypt messages both for me and the people I was talking to, requiring both parties to regularly need to re-send messages until they finally unencrypted properly. This made it a real ball-ache to use, as you could send a message, and then hours later have someone else say they can't read it. I'm also not a fan of how much Metadata it spreads around.

XMPP on the other hand has always been snappy and fast, and I much prefer the clients available for it. It's currently the most promising federated option, IMHO, with Movim being the most promising client as a Discord replacement.

It's still missing some essential Discord-like features, such as groups of rooms in a server and drop-in voice rooms, but both features are being actively worked on, and a funding campaign was started to accelerate development.

But what it can do already is:

• Excellent text chats, including with very good optional encryption
• Group voice/video calls with screensharing (must use a chromium based browser to screenshare an app's audio)
• A neat integrated blogging feature for communities & individuals
• a built-in paint program to draw stuff to input into the chat
• Full working and proven federation thanks to the XMPP back-end

Xmpp. Looks less polished, but works better, and isn't mostly controlled by the ex-Amdocs Matrix Foundation.

Fluxer is a better Discord alternative than Matrix and XMPP.

That said, XMPP is more private. Matrix is worse than everything else.

Why has IRC not been mentioned? The basics of Discords UX is based on it after all.

From my digging on alternatives the main contenders are (in no particular order)

• Stoat
  • Essentially 1:1 on discords format
  • UK based, so its future there is uncertain
  • Infrastructure is lacking, was crippled by the initial influx after discord's announcement.
  • Missing some minor UI and UX features, feels unpolished.
• Spacebar
  • Reverse engineered discord
  • Greatest potential, IMO, but as of a few days ago all it has is potential.
  • lacks significant client development, relying on an external client named Fermi, which feels quite amateurish.
• XMPP
  • Highly mature, looks very promising, but lacks any kind of guild/nested channel grouping support which makes it unsuitable for my group, so I didn't look too deep at it.
• Matrix
  • IMO the most likely discord successor.
  • Minor functional hiccups, that vary from client to client
  • Of the clients I tested, Cinny is the most discord like, but I hear commet is closer.
  • Nested spaces provides the minimum format equivalence.
• Fluxer
  • Slightly sus vibes
  • Lacks self hosting instructions
  • Media is non-permanent, which is I guess fair to keep infra costs down, but its unsuitable for my groups media usage habits.
  • Looks promising, but I've not actually tried it given the lack of self hosting instructions.

One thing that's wormed its way onto the to do list that haunts the back of my mind, is I'd like to see if I could abuse the matrix or XMPP protocols to get some of the nicer discord-like features lime invite links, server side channel ordering, and space membership over channel membership. But that's unlikely to happen any time soon.

EDIT: Forgot Fluxer. Added.

The problem is that "Discord" means something else for almost anyone and there is no alternative that 100% covers all the usecases.

For many public chats, IRC with a modern server and client is perfectly suitable, and for my private gaming sessions Mumble is as voice chat is doing fine even though friends are complaining that they can't just use it in a browser.

For general IM stuff XMPP is best, but I guess few people use Discord for that. Matrix is in general slow and clunky, no real point of using that except if you are forced to because some very specific FOSS projects insist on using it.

P.S.: I mostly use IRC through a XMPP gateway.

IMHO XMPP is far more architecturally sound and not driven by buzzword-development.

I prefered xmpp. But either xmpp or matrix arent discord alternatives

Having installed both this week, I much prefer XMPP. I want it as something more like signal/whatsapp just for my immediate family. Some are too young for a phone number, but I want them to join in the fun.

It was a but of messing around getting prosody to work how I want, but I'm really happy with it. It works with my letsencrypt certs. Phone and video calls just work. MySql just works with it. The tricky one was getting it to auth with same credentials as the mail daemon, but I got that going too. It's seamless now.

Matrix was 90% features I would not use.

I also prefer xmpp, which I find more stable and easier to set up and maintain.

In my experience XMPP is easy to set up, lighter on resources, and the clients tend to work well across multiple platforms. We have small private and public groups using it daily with zero complaints.

Matrix tends to be more involved in setting up, and our group ran into issues where some clients weren't working as smoothly or reliably as we needed for a primary communication platform. We also had a huge problem with traffickers of all sorts joining our rooms to spam their telegram links or CSAM. That hasn't been a problem after more than a year on XMPP.

Do you prefer XMPP or Matrix

Yes* - I haven't used Discord in a long time as its bloat simply doesn't interest me, but for communicating with folk:

Matrix, at least for me, is great, but the most capable mobile client Element has many broken or missing features.
Classic, but not X, has:

• working calls via STUN/TURN,
• an emoji menu,
• correctly showing chat profile images (X duplicates the most recent one for all chats),
• and the ability to create unencrypted group chats (purely for public memes).

X, but not Classic, has:

• attachment captions,
• HD images,
• markdown support,
• a more modern UI,
• and (when it works) fully encrypted 1-1 and conference calls via Matrix Livekit.

I currently dual-wield the two because neither is enough yet, and most other clients lack call functionality entirely.

XMPP, at least for me, is nearly perfect. It just works and I find the fact that desktop clients still look like AOL Messenger quite charming. However it has:

• very manual encryption key management, meaning even I find trusting a new device daunting let alone any adopters,
• no backward decryption, meaning message history needs to be exported and transferred to a new device,
• plaintext serverside storage for several pieces of data. It's my server so ownership isn't a worry, but it's a massive security risk in the albeit unlikely event of a hack or hijack.

I chose higher encryption and easier adoption between Matrix and XMPP but wish there was a more fulfilling option.