I'm in Emacs 99% of my day, and I don't think I've ever used the function keys inside Emacs.

All my volume/brightness/etc functions are handled on a separate layer. I've got function keys on another layer as well, but I don't ever use them.

If you use function keys a lot, then you could do something like putting the function keys on one layer all on the right hand like it's a num pad and then adding a key on the left hand to switch to that layer. You could add combo-taps on your main layer to trigger the function key (e.g. press `q` and `1` at the same time to hit `f1`, `w` and `2` at the same time to send `f2`, etc.), etc. etc.

QMK gives you a lot of options to do what you want. There's also 3 keys towards the center of the keyboard on each side that I rarely hit (in fact, they're used for some layer switching some times!) that you could easy bind to function keys directly.

Note that a key can do like 4 different things depending if you tap, hold, double tap, or tap and hold if you want to get really fancy.