I had an issue where one keyboard (worked with another one) worked in bootloader, but not when entering the encryption password after that. I believe I solved that by moving keyboard earlier in the module list in mkinitcpio.conf. Maybe something similar would solve your issue?
I feel like there is going to be a disproportionate amount of people not using a standard qwerty keyboard that replies to this :)
I use qwerty on a standard 100% and another split 60%. I am trying to switch to ortholinear split Dvorak, but haven’t been able to design a keyboard I am comfortable switching to full time. I would also need two of them, one for home, one for work.