Raspberry Pi 500 uses QMK Firmware for built-in keyboard
jeffgeerling.com
jeffgeerling.com
Once it becomes generally available an in people's hands, I hope someone will post a generic firmware image with just these things added.
I think it is great that it is programmable. This means also that replacement keyboards with more keys/functions is a real option. I've seen a couple projects using the Pi 400's PCB with a mechanical keyboard but those have either hooked it up separately via USB or been limited by the original keyboard's matrix.
Personally I've been sketching on an Amiga-inspired mechanical keyboard for a couple of years and wanting to put a Pi in it.
[0]: <https://github.com/raspberrypi/QMK/tree/pi500/keyboards/rpi/...>