https://www.ifixit.com/News/50450/samsung-galaxy-upcycling-u...
To be honest, it sort of makes sense, why would they want to open themselves upto unlimited brand damage liability from battery fires, while spending untold amount of man hours porting mainline linux onto obsolete platforms they'll never see a cent from anymore - whether it be in other products or through services revenue.
I've repurposed an old Galaxy S7 to run as a remote development server, via this method. I have it set up so it's just like logging into any other Linux box.
https://forum.xda-developers.com/t/patched-odin-3-13-1.37625...
do note, the patched out safety checks will definitely allow you to shoot yourself in the foot if you flash the wrong images
Sounds like the US would benefit from some EU style legislation.