I’m also a recent transplant. I too find the (current) lack of activity in certain niche areas disappointing, but I’m hoping that’s temporary. I hope discussions of some of those topics can survive the inevitable fragmentation among instances.
On the other hand, I’ve installed Jerboa on my phone, and it’s working very well. Now I’ve just got to get busy participating in those niche communities–could be tricky, 'coz the ones I often liked best were the ones I knew the least about. I enjoyed learning from people who already knew the ropes.
How so?