Night Light works system-wide for me, including the lock screen. Samsung Chromebook Plus, single user, stable channel. If yours is bugged, perhaps setting a dar

Night Light works system-wide for me, including the lock screen. Samsung Chromebook Plus, single user, stable channel. If yours is bugged, perhaps setting a dark wallpaper background might help mitigate the issue? The rotation lock, I can't say I've had any issues with it, but I don't think I use the Chromebook Plus in tablet mode nearly as much as it sounds like you do.