InfinityBook S 15 - Gen6 got stuck in reboot

Hi, I wanted to reboot my InfinityBook S 15 - Gen6 with up-to-date Ubuntu. Now it seems to be off (no fan, no heat emission) but the two green LEDs left and right of the power button are still on. I can press the power button short or long, nothing happens. The power cable was plugged in when I started reboot. I unplugged it meanwhile. I wanted to reboot because while streaming a video suddenly the stream got interrupted every few seconds while Wifi was excellent. At that time I wanted to change the keyboard light with the Fn keys, but that stopped working after few key presses. I'm not sure if I started that before the video problems or while I waited for the video to load the next few seconds. I'm mentioning the keyboard light, because I read that others have problems with that, too. What could I do (except taking the screwdriver and trying to detach the battery)?