Well I still don't think it is out of scope then for just the NUT client for enterprises or HomeLabs on XCP-NG.
SBCs are everywhere these days. Using a Raspberry Pi as the NUT Server in a homelab or a flavor of a more robust server for NUT seems like a solid choice. No USB passthrough to worry about, uptime on a 1500VA+ UPS, forget about it! There are a handful of guides how to get it running for a Pi or anything else (including this post).
As I think this though, I would still feel ok with another external device watching, waiting, and notifying me on a successful power off of any number of my hosts and VMs. Not all enterprises or homelabs can afford (even if their appetites want it) to get enterprise level power automations. We have our power. Break the chain. @olivierlambert