Okay, since days I am trying to find out what problem my installation has. It's weird. I used the old hyperion since years on a lightberry config (Pi 3, adalight apa102) without any problems. Recently I switched to hyperion.ng. I installed Hyperbian, smaller problems with my default user not being pi were resolved easily.
Everything works fine, except that often there are no LEDs lighting up. I found some threads with similar problems and tried everything, like disabling bluetooth, checking permissions at /dev/ttyacm0, switching usb slot, playing with the baud rate. Nothing really helped. The thing is: after 3 to 5 reboots (without changing anything!) it works perfectly fine. Restarting hyperion only (sudo systemctl restart hyperion@micha) does not do the trick. At times I thought having found the problem, but it was just the rebooting that solved it. As soon as it works, I can reboot and it will still be working fine.
The problem only seems to show up after a cold boot only, when I switched the pi off the day or hours before. It's reproducible all times. Most of the times after 3 reboots (sudo reboot via ssh is enough) everything works fine. I am out of ideas, what the problem is. In one thread with a similar problem (leds not working at all) I've read, someone wrote that updating the arduino with latest firmware from lightberry had worked for him. Problem is, the given link to lightberry page is no longer available.
I will attach two debug logs, one of it when it works, one of it when it does not work. As mentioned before: Nothing changed between these runs. Only some reboots.