Mac users have problems with Fn keys, its not easy to use them in far2l. They often ask for special mode then Esc and numeric key pressed simultaneously emulate Fn keys.

But even in mc this feature doesn't work reliable. It requires saving a number after Esc or after several consecutive Escs, and then canceling these Escs.

I suggest considering other possible solutions:

1. Like with *, + and - keys, map 1..0 to F1..F10 if command line is empty (if --mapnumkeys, for example, is specified)
2. Map Alt+Shift+n to Fn. This combinations are quite non-intuitive and probably will never be used for any other goal