This product: https://www.logitech.com/en-us/product/wireless-touch-keyboard-k400-plus?crid=27
has a bad habbit of function keys being disabled by default.
So, here is ad hoc solution working with /dev/hidraw*
Since it is just small script for my convenience, it iterates: /dev/hidraw0 /dev/hidraw1 /dev/hidraw2
And it it finds suitable product, sends message to device, after which function keys start to work properly
One can uncomment
#fkeys string to enable pressing FN key back
and enhance
for i in ['0','1','2']:
with addtitional numbers that are added to /dev/hidraw[i]
since I have feeling, script catches ReadWrite exceptions, this is also place to put proper values there.
Suitable devices can be listed with
ls /dev/hidraw*