I am happy with social.tchncs.de Edit: The only relevent part: it is well moderated. The rest i solved by following hastags and people
SECUSO developed some apps i enjoy the notes app a lot. It also does to-do lists. Just add search for Notes (PFA). Its really basic.https://secuso.aifb.kit.edu/105.php
Some things Apple FindMy does was solved by KDE Connect for me. Not sure about a Location Sharing service.
I am happy with social.tchncs.de Edit: The only relevent part: it is well moderated. The rest i solved by following hastags and people