Looked around for a while now, these are the alternatives I found.

• Zulip: More like a Slack alternative for an organization/team/group, can be self hosted, seems to be pretty mature and well made. Has good client apps. No screen sharing/voice chat.
• Stoat: Seems to be mostly similar to Discord, doesn't seem mature though, self hosting documentation doesn't seem refined, could be okay if you use their server, not sure about mobile apps
• Spacebar: 1:1 Discord clone, voice chat features seem to be incomplete but seems pretty good otherwise, I tried to install their server but it doesn't run for me..
• Matrix: Feature complete, but kinda buggy, may work well enough for some but my friends complained for poor UX
• Mattermost: Gotta self host or pay, there seems to be some weird limitation: https://news.ycombinator.com/item?id=46861331 and https://news.ycombinator.com/item?id=46594673
• IRC: maybe not for non-techies, but IRCv3 has some "modern" features and Goguma(Android)/TheLounge(Web) looks quite decent
• XMPP: Seems like it should be good, but I'm having trouble setting it up so can't tell
• Tailchat: UI looks just like Discord, but I just heard of it now so haven't tried

do you know if stoat's ios client good enough? last i tried the android one was also very basic.

isn't it just a webapp? should be trivial to package as a 'standalone program'

they don't have screen sharing :/

Riot renamed to Element.io, Revolt renamed to Stoat.chat

personally i'd also backup the messages before deleting, this works well https://github.com/Tyrrrz/DiscordChatExporter

their ui was perfect. why can't we have nice things..

seems like they had a decent name 'revolt' but got some cease and desist and didn't resist and decided to switch.

has anyone tried their iOS client? from their description it seems like it's less mature than the android version, kinda concerning as my friend group has some iphone users.

could you recommend a good xmpp setup? i heard good things about snikket, maybe something else too?

may i ask which homeserver and client you use? it seems like synapse and element is not the best choice especially for small number of people.

if this is for privacy i'd just use the cheapest/fastest option that supports rclone and use its encrypted upload feature.