Where is the .ROM file stored? How do we back it up for future BIOS flashes, if the BIOS gets corrupted?
You need to use flashrom to do so:
flashrom -r backup.rom -p internal
If you have a permission issue raised, you need to add boot param iomem=relaxed
Keep in mind that if the flashing fails and you reboot, then the laptop will not boot anymore and your backup file won’t help (need to think of your restore procedure if you want to take backups…)
Although, that coreboot flashing is usually reliable. I had used purism scripts for coreboot upgrades on my 2 librem 13 laptops and never had any issues with it.
That said, there are failure modes for a BIOS update that are not catastrophic i.e. you want to downgrade and you can downgrade, for example, because the new version exhibits some nasty problems but not so bad that you can’t downgrade (not bricked).
If I’m using Qubes do you know how I would install flashrom in dom0? Or does it work outside dom0?
Qubes and those domX are all about isolation through virtualisation so flashing must be done via dom0.
Usually hypervisor solutions present a BIOS emulation to their guests and not the real BIOS supporting the actual HW so flashing from non dom0 would probably fail or just have no effect.