Thank you for this, it pushed me to not give up!
I manged to get Qubes to boot in Legacy mode so I figured it was a UEFI configuration issue but changing BOOTX64.cfg to every concievable option only caused varying errors.
Ultimatly I got UEFI working with the default BOOTX64.cfg settings by enabling Legacy Boot in the BIOS. This I found really weird. I was definitely selecting UEFI boot in alll incidents and here is what happened:
- UEFI boot from USB wiith Legacy Boot turned off in BIOS: Get white messages on black screen but then screen goes black and freezes.
- UEFI boot from USB wiith Legacy Boot turned on in BIOS: Boots to installer and allows me to install Qubes.
*UEFI boot to SSD with Legacy Boot turned on in BIOS: Boots, allows me to unlock the drive then works.
*UEFI boot to SSD with Legacy Boot turned off in BIOS: Boots to the moment just before asking for passphrase to unlock drive then screen goes black and freezes.
So I guess this resolves my problem as long as I leave the Legacy Boot option enabled. I’ve now got to deal with extra problems of the embedded NIC and graphics not working with kernal 4.8.5 so need to update this using a USB NIC apapter!
Thank you to @ludovic for all the detailed information.