This is great to see, thank you for taking the time to rescue this; and thanks to @john.c for the recovery work and to @tjkreidl for writing it in the first place.
I went looking, and there is a small XCP-ng-specific piece on this in the official docs under NUMA affinity (https://docs.xcp-ng.org/compute#numa-affinity), but it's nothing like the depth of the Tale of Two Servers series, so having the originals archived is genuinely useful.
I won't pretend to judge how much of the 2019 BIOS and GPU-scheduler guidance still maps cleanly onto current hardware and XCP-ng versions; others here will know where it's aged and where it hasn't.
I'll make sure this is on our radar on the docs side, because it keeps coming up. Really appreciate you keeping this from disappearing.