Thank you for your answer!
For power supply I am using a https://www.anker.com/products/variant/powerport-speed-5-ports/A2054111 and tried both the QC ports and the so called “IQ” ports.
The “normal” Android image seems to be working, though I did not test it extensively, but with that image youtube-videos do not start playing neither in the youtube app, nor in firefox.
If you are interested in fixing the problem I can continue to try and provide information. Please send me what information you need.
Otherwise I will be trying to get the linux image running better, as I did not get it to play hardware accelerated video in browser yet (for another topic).