How to set keyboard layout on wayland only machine

https://nixos.wiki/wiki/Keyboard_Layout_Customization

Unless you have a definition somewhere else in your config that would override the system default keymap, you should retain your current keymap. It should also be noted that Wayland can run along side xserver. Refer to my other answer to a similar thing in another post: Add custom resolutions - #5 by DinnerBug