I do not know how to get this point through: T400/T500/X200 are not fit for Qubes OS.
People have confirmed this, even in this thread, quoted just above, here.
This post is a duplicate of another post on libreboot. Libreboot devices are not fit (platforms too old to have vt-d2, see Qubes OS requirements) to have users benefit of hardware isolation it offers.
That duplicate post:
Refers to a github issue, where Zammit says:
“By the way, I submitted a patch ages ago to fix DMAR table in X200, so VT-d1 works on X200 with coreboot and no ME, see https://review.coreboot.org/#/c/16330/ … also, there might be some way to fix the graphics corruption on IGD if someone considers pursuing my old patch that got abandoned: https://review.coreboot.org/#/c/17645/”
So there will were still graphical glitches when using Qubes 3.2. Fixes should happen first in coreboot for it to deal with that known problem.
Also, having had to change things under Heads for it to be able to boot 4.1, VBT blobs also need to be injected in coreboot for it to have the installer boot properly.
xx20 can be beautiful machines to boot Tails from USB sticks. But Qubes OS, it never really worked, and making it work today is a bit pointless without the platform fitting Qubes OS System requirements
If libreboot is desired, I think the only platform supporting Qubes (not even sure, untested. Would need to be confirmed.) is the G505S. But it is rare, not so well constructed (people said) and not having a TPM either. Not a requirement, again, but also have lost interest in trying to support it under Heads.
@222 I tested x200 with Qubes for 3.2 support a while back.
libreboot says it themselves
Where “Anecdotal reports from at least 1 user suggests that some models with CPU microcode 1067a (on the CPU itself) might work with vt-x in libreboot”. That was me.
If you could ask Leah from libreboot to make a note saying that libreboot xx00 are not compatible with Qubes OS because lack of vt-d2 and vt-x, that would be a service to both communities.