The new 4.2 version of #Mastodon includes significant improvements in the search function!
My favourite one, which I've been using a lot lately to find new people to follow, is that profile search now works on bios too and not just the user name. So if you type, say, "astronomer", "scicomm" or "journalist", you'll find people with those words in their bio.
And the opt-in full-text search for posts, with operators, is also great!