Selfhosted

I use Matrix with the Jitsi plugin. I know everyone talks shit about Matrix, it's been flawless for me.

IDK about watching videos, that's a lot to ask of a screensharing app.

Element on Matrix is the only one I'm aware of - but it's not the easiest to set up. I would try creating an account on matrix.org's server just temporarily to try it out and see if it fits what you're looking for. I like the decentralized nature of it, but the support is very piecemeal, and onboarding people essentially needs a class.

Perhaps Spacebar is a thing (the client of choice would be Fermi I think). Didn't try it myself yet though, I do not know about how well its security protocol works. I'd assume it uses just a standard TURNS server for audio and video though.

Then of course there's Matrix with Jitsi plugin, which will give you persistent headaches and a new appreciation of touching grass. It's a mess, but hypothetically offers E2EE (if it works).

This isn't necessarily an answer, but what ever happened to Revolt?

I currently have a Raspberry Pi 3 B+ but I'm aware it's a bit old and is ARM so I'm thinking of buying a Pi 5.

The Pi 5 lacks a H264 hardware encoder/decoder, making it unsuitable for most streaming/transcoding purposes.

I’m using TeamSpeak. It is very good and feature rich, but it’s important to note that video / screen sharing works only P2P in a moment, so no server processing. It’s probably ok if you don’t have more than 3 people in a party, but still worth noting.

I also tried Matrix + Element + Jitsi. Can’t recommend.

To my knowledge there is no such thing available however you have just enlightened me about TS6's featureset. It sounds like it is the exact solution you are asking for (and one I'm going to immediately try out myself.)

Tried NextCloud with Talk module?

Encrypted Matrix or mattermost server with jitsi?

We all use Signal already for messaging but it just doesn't fulfill our screenshare needs.

...why not?

Most important feature it needs is the ability to screenshare with system audio, such as for streaming games or watching videos.

It has that. Have you tried their videoconferencing feature?

Other than that you can use one of a million Jitsi instances (Element has a publicly available one). Personally I use MiroTalk.

Galéne, but it's really only for video/voice chat. But that it does great, low resource use, and you can even have multiple media streams from the same machine without issue.

I've streamed games to friends over Signal. Why won't that work for you?

There is also Peersuite which is a P2P solution and offers great audio and streaming quality. However, it is mainly a single developer behind it and it hasn't received an update in months. It still lacks some polish and features like a server instance and persistent chats and rooms.

For me, this is the most promising one I have come across in terms of a replacement for Discord.

https://movim.eu/ can do that AFAIK, but for now the A/V calls don't go through an SFU distribution server (coming soonish), so it will not scale to many participants. But if you want to only stream to a few people (like max. 5 or so, depends a bit on your and their internet speed) it should work.

I've been trying to get zulip working.

Sounds like it addresses your requirements.

Seems to be a real bitch to self host - I've been doing this a while but the compose yaml is pretty arcane with hundreds of environment variables.

I didn't "give up" exactly but it's been on the back burner for a month or so now.

Matrix with element call works well however I don't think audio works with screensharing but you can work around that by routing desktop audio through your mic input or have a separate acc for screensharing audio it not the best but imo its the closest to discord. Hopefully soon audio will work.

I use self-hosted Jitsi for screen share, although this is just video conference software without the IM aspect of Discord. (Jitsi does have IM to be clear, but it's a chat tied to a particular meeting, not like a persistent groupchat.) You could just use Signal chats as you have already been doing and send Jitsi links when you want to call. Jitsi has E2EE although I'm not up to date on the details of how it works.

I really love all my various Pis but at the moment there are so many refurbished servers available (thank Windows 11) as well as several small form factor x86 PCs that a Raspberry Pi 5 sadly is on the lower end of performance/cost.