I am looking for a way to replace the stock lock screen (with an app, not a rom). What is the best way to do it, for a start to disable the lock screen on as much devices as
Try this, it will keep awake the screen/ display , as long as the activity is on top.
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
Also this does not require any permission in manifest.