Mapping upper left esc key to fn

Is it possible to map the upper left esc key to fn? How? Apparently xmodmap is deprecated and you should use something like setxkbmap instead. I tried something like:

xmodmap -e "keycode 1 = 464"

where esc has keycode 1 and fn has keycode 464, but I got the error:

xmodmap:  commandline:1:  bad keycode value (out of range)
xmodmap:  1 error encountered, aborting.

System information:

Linux 5.19.0-46-generic #47~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jun 21 15:35:31 UTC 2 x86_64

(Kde Neon on a Macbook Pro 2015).