Greeeeaaat question!
Been thinking about this problem a lot and what I'd prefer myself is: 

1. You can only post chat messages to 1 group
2. But you can publish posts, articles, wikis, docs, books, git problems, etc... in multiple groups at once 
3. You can determine per group what you get notified about on your home screen
https://cdn.satellite.earth/62e3437aba0b4e51d8231807344ef056079a6a845a91594688910cde52e9b6ee.png
Since I'm giving every category an emoji-icon in the group's menu, I can reuse these as a compact way of displaying the telegram-like counters in the home screen. 
https://cdn.satellite.earth/f0b0f7d32302f4772c3128a4d97ab5897d54cf50a66499e2f669a36a6d0d879e.png

4. The home screen let's you open feeds by content category (posts, articles, ...).
https://cdn.satellite.earth/3d53d9393a6369940a33938ab9880971a078447153a56ee0c0f10860bf6e82a3.mov