I updated my keyboard firmware using gnome-firmware. This (as expected) reset my keyboard to the original layout. So I consulted the operators handbook and followed the steps there instead. The firmware built fine, but then would not flash, with error message “No device in BOOTSEL mode found at bus 1” (I tried it with and without the keyboard being in firmware update mode before running the flash command). Has the method for customising the keyboard layout changed since the handbook was published?
Nevermind. I put the keyboard into firmware mode, turned off the -f flag for safety and then just tried different buses until one of them worked