@AzureKingfisher If you don't mind it being closed source, take a look at Discord or Slack. The latter however locks your history after 10k messages unless you pay a subscribtion.
@Kiki but slack is instant messaging /chat groups based on IRC, right?
@AzureKingfisher Not sure if it's actually "based on", but yeah, it feels similar to irc. With the big exception that you always get all messages when you're offline. You need to actively leave the server, and I think that's a big plus.
Also, there's calendar integration and add-ons for polls and stuff and lots of other connectivity.
Nextcloud https://nextcloud.org/ could add the rest. (files, calendars, decks, etc.)
Both free/libre hosted (nextcloud paid, Matrix gratis) & self-hosted.
@AzureKingfisher If they actually want to improve something, get a hosted Nextcloud Instance and obtain a descent level of privacy and security in return.
If the people are unwilling to learn anything for improving their situation… abandon ship.
I can only outline a very good and usable solution.
chaos.social - because anarchy is much more fun with friends.
chaos.social is a small Mastodon instance for and by the Chaos community surrounding the Chaos Computer Club. We provide a small community space - Be excellent to each other, and have a look at what that means around here.
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The primary instance languages are German and English.