Trouble installing QubesOS from USB

[apparatus]

Can you access the console on another tty?
Did you try this?

@apparatus

You can try to switch to another TTY using Ctrl+Alt+F1 - Ctrl+Alt+F12 when you’ve reached the Starting lightdm.service step to check if the system is accessible but only GUI is not showing up.

If you can then you can disable the Nvidia GPU there without mounting the Qubes OS dom0 root in another system.