Matrix is definitely more private than discord. Although it does still leak a lot of meta data. If even that is a concern then a simplex group is about all that there is left.

Chachi and Flotilla. nostr:nprofile1qqs8lft0t45k92c78n2zfe6ccvqzhpn977cd3h8wnl579zxhw5dvr9qpzemhxue69uhkvun9deejumn0wd68yvfwvdhk6qgdwaehxw309ahx7uewd3hkcqghwaehxw309anxjmr5v4ezumn0wd68ytnhd9hx2aezugp and nostr:nprofile1qqsf03c2gsmx5ef4c9zmxvlew04gdh7u94afnknp33qvv3c94kvwxgsppemhxue69uhkummn9ekx7mp0qy2hwumn8ghj7un9d3shjtnyv9kh2uewd9hj7qgewaehxw309a5xyu3wvdhhyctrd3jjuum0vd5kzmp0gankr4 can make any changes you want.

If I'm honest, I'm using Telegram most often for that sort of thing. Also logged into IRC, but Libera and OFTC are both mostly dead these days. Not sure what server the cool kids are on.

With matrix you can bridge the same chat to discord, telegram etc so minimal onboarding required

IRC with perhaps thelounge or glowing bear for a slightly better experience

Matrix is cool, perhaps even consider rocketchat mattermost.

Or something the nostr devs are coding up if you’re ok with a wip tool

Matrix. They have lots of clients for people to choose from whether they use desktop, mobile or just want to use their browser. It can have end to end encryption if you want

Check out Keet by Holepunch. https://keet.io/

It’s not there quite yet but hopefully White Noise will be the app you’re looking for.