[mightykan]

An alternative to Zulip is Twist - https://twistapp.com. (I'm not affiliated with them at all; just a fan.)

They have a proper native (as in not Electron-based) Mac OS X app (probably other platforms, too, but I haven't checked), which launches almost instantly and consumes a very reasonable amount of RAM. It's definitely worth a look.

[pritambaral]

For others like me: No Linux app.

[piotrkubisa]

It reminds me the Zoho Streams [0] feature in their Mail service.

0: https://www.zoho.com/mail/streams.html

[Fedoranimus]

I'm a big fan of Twist and most things that Doist does in general.