in the spirit of this post, but from the other side

I have a shitdroid that I can't root because the vendor sucks, but google can go fuck themselves too. combined with that I haven't androided much for about a decade and know nothing about the current ecosystem.. I'm looking for good alternatives to a few things. free/foss preferred but I'm pragmatic over picky - if there's a good paid option I'm willing to consider it

immediate known requirements include contact sync, calendar (more business than personal but either works if it's good). maybe also other things I should know about?

judicuous preference to things that support open protocols and self-hosting (i.e. anything that has to use their service to operate - no go)

tell me about good apps! I know about syncthing and photosync