If by flavor you mean linux mint: yes, absolutely! If you mean anything else thats more like ubuntu itself: hell no!

Yes you can since ever. When in your feed just tap on the middle too and then again on community…

Memmy so far, but Mlem starts catching up. Memmy has more active devs tho. I feel like Limbo is not as developed and seems to be a inspired by the „original“ reddit app. Thunder seems nice too, haven’t tried that much so far but definitely inspired by Apollo as well.