Qubes OS does not start after enabling sys-usb when it is installed on a USB hard drive

EDIT:

This post/solution is helpful if:

  1. Your system is installed on a USB HDD/SSD and
  2. Your system does not start up after you enabled sys-usb

ORIGINAL:

Yesterday I enabled sys-usb. In hindsight, that was a bad idea since that caused my USB peripherals to detach and I wasn’t able to find my PS/2 mouse and keyboard. So I had to shut down the system ungracefully.
Today the decryption prompt did not show up and after a while I was confronted with this screen.

I have backups though. Is there a chance to repair the system or should I just reinstall? The LUKS partition looks healthy.

Did you install Qubes OS on a USB disk?

Yes! A sATA drive connected via USB3.

I see where this is going…

Disable qubes autostart so sys-usb won’t start on boot:

Also remove the rd.qubes.hide_all_usb and usbcore.authorized_default=0 kernel command line options in GRUB if you have them.

Then check this:

Thank you for the great and quick support!