Some #fediverse #mastodon servers popping up more than others (beyond the main, large ones), not surprisingly given my interests:

https://drosophila.social for scientists working with the vinegar fly, #Drosophila, the genetic model organism par excellence.

https://fosstodon.org for FOSS: free open source software developers.

https://mathtodon.xyz for mathematics and physics. Famously @johncarlosbaez is hosted there.

https://scicomm.xyz for scientific communications, public outreach.

https://photog.social/ for photography, "3-5 photo posts per day recommended to avoid overloading the timeline" and no-nonsense.