Haven’t tried it yet, but if you haven’t rebuilt the wheel already I think this might work. GitHub - sezanzeb/input-remapper: 🎮 ⌨ An easy to use tool to change the behaviour of your input devices.
Edit: Alright, I’ve tried it myself and it doesn’t work in PostmarketOS.
BTW, if anyone’s trying to get shutdown commands to function in SwayWM under PostmarketOS (which doesn’t have systemd), loginctl poweroff works.