I use the built-in `hidutil` utility to remap F3-F9 to my preferred keys.

F3/F4 are remapped to the keyboard backlight brightness.

F5-F9 are remapped to be plain old function keys.

This post has a lot of great info: https://news.ycombinator.com/item?id=35555475

This is the mapping I use on an M1 MacBook:

    hidutil property --set '{
      "UserKeyMapping":[
        {"HIDKeyboardModifierMappingSrc":0x0000FF0100000010,"HIDKeyboardModifierMappingDst":0x00FF00000009},
        {"HIDKeyboardModifierMappingSrc":0x0000000c00000221,"HIDKeyboardModifierMappingDst":0x00FF00000008},
        {"HIDKeyboardModifierMappingSrc":0x0000000c000000cf,"HIDKeyboardModifierMappingDst":0x00070000003e},
        {"HIDKeyboardModifierMappingSrc":0x000000010000009b,"HIDKeyboardModifierMappingDst":0x00070000003f},
        {"HIDKeyboardModifierMappingSrc":0x0000000c000000b4,"HIDKeyboardModifierMappingDst":0x000700000040},
        {"HIDKeyboardModifierMappingSrc":0x0000000c000000cd,"HIDKeyboardModifierMappingDst":0x000700000041},
        {"HIDKeyboardModifierMappingSrc":0x0000000c000000b3,"HIDKeyboardModifierMappingDst":0x000700000042}
      ]
     }'