I read through:
https://www.qubes-os.org/doc/uefi-troubleshooting/#f1
But I can't even get to the grub menu
and if it's the problem further down "Boot device not recognized after installing" I don't know how to get to those files and copy them when I can't even get to a terminal.
You can enter a Qubes Rescue Mode via your installer USB Boot Menu. Maybe this problem ? :
https://github.com/QubesOS/qubes-issues/issues/2381
regards
yes I eventually figured it out. Booted from the USB install and mounted the quebes install and did the changes in the troubleshooting tutorial and all worked fine.