Open source related application, for open source desktops like Linux (unfortunately not for open source Android/GrapheneOS currently), there's Alex Harsányi's ActivityLog2 (which is an impressive application in Racket):

https://github.com/alex-hhh/ActivityLog2/wiki/Just-The-Scree...

Incidentally, I'd love to have an open source, privacy-respecting nutrition tracker that works on open source desktops. (I find my laptop much, much faster than phone for recording this data, at least in the ad hoc way I'm doing it, including things like weights of every ingredient that goes into a dish.)