When talking to @joakim_s regarding emus he suggested to open a thread regarding PS3 controller support.
Connecting via USB should work out of the box with a recent kernel, at least it does in Ubuntu.
I‘m not familiar with the Linux input stack, maybe only some udev rule is missing.
Bluetooth requires the sixad service installed and running.
LibreELEC seems to have both out of the box and might be usable as a starting ground.
I can supply logs and do testing.
Thanks!
Mod: Vero4k(+)