@francis-r The ipxe.efi/undionly.kpxe manages the FOG boot menu. Once you make a selection then bzImage and init.xz are loaded then its “the kernel” that is in charge. So if you have issues selecting things or entering passwords into the boot menu then its iPXE that needs to be refactored. I know I’ve recompiled ipxe in the past with an alternate keyboard. So its possible. FOG has the programs already installed to recompile ipxe all you need to do is just update the keyboard config file to use something other than US english.
Here are the instructions for recompiling iPXE using FOG: https://forums.fogproject.org/topic/15826/updating-compiling-the-latest-version-of-ipxe you will just need to find and update the config file