is a way to use the leds on the APU4C4 on OpenBSD 6.5, gpioctl ?
If I understand correctly, the LEDs are controllable via gpio(4)s. In principle, you can do this via gpioctl(8).
You cannot control the GPIOs on J20, because those are are driven by a NCT5104D and wbsio(4) only supports hardware monitoring.
The LEDs OTOH are on GPIOs of the AMD FCH. I am not a hardware guy, and OpenBSD seems to have a lot of drivers which attach - but probably none for those GPIOs.
If you want to dig deeper, there is AMD documentation for the FCH and also a linux driver called "amd-fch-gpio"
Update: There seems to be somebody, who worked on this a while ago on OpenBSD: https://marc.info/?l=openbsd-tech&m=155355977613046