I knew I saw it already somewhere though, finally found - https://mastodon.social/@mntmn/105753560212021418 , took me two days to find. Also no need in hidapi as it could simply be fed via /dev/hidraw. On the other hand I can do hidapi now, which I need for nitrokey hotp
this result was generated by executing this code https://gitlab.com/rufferson/mntkbd with this shell command
for r in 1 2 3; do for i in 1 4 8 16 2 0; do sudo _b/mntkbd LEDS$i 1; done; sleep 1; done
sudo is needed to access evdev input device.