I'm apparently a victim of the common bug in newer kernels which disables keyboard and mice right after gui startup, as seen on Ubuntu 20.04.1 LTS: laptop keyboard not working after updates Ubuntu 20.04.1 LTS: laptop keyboard not working after updates
This could be probably solved by using an older kernel or by some grub magic, but I have not installed Ubuntu on the device yet thus I am not able to edit any parameters or software on the live installation usb stick. Any idea, how to even install Ubuntu over this bug?