[2022] How many specialties can I get playing for 1 month actively like 5-8h a day ?

That depends on on the collaboration settings, with double high collaboration you'd get 6-7 if you optimize food and housing all time (if you don't, you get much less). With lower collaboration settings, you can get 2 - 4 times the amount.

Sea Otter uses normal high collaboration, but meteor is only 21 days there. With optimized efforts you should be able to probably get around 10.

You were playing on an official server, they do have the guaranteed runtime of the server as dates in their server name :)