I've been "upcycling" my SGS3 for years now using it as our family primary smart Music player in the living room. But this "upcycling" initiative really grids my gears, because Samsung has locked it's phones to ancient versions of Android, making them artificially obsolete and insecure. So on the one hand they're artificially making hardware obsolete, and on the other hand they're pushing their old hardware for stupid ideas like bitcoin mining. I know people that have a drawer of old smartphones and still wasted $50 on a Google Mini. Off the top of my head, can think of so many better uses than mining.
* Dedicated home VoIP phone
* Home Music player
* Home Media player
* Google Mini / Echo Dot
Most old smartphone are perfectly capable of any of the above, especially if manufactures unlocked them to allow CyanogenMod/LineageOS