@planedrop Thought you might be interested to hear my results... The Vendor A) refuses to talk to me since I'm an MSP and not a direct employee of my client... Stupid, but I sent questions to my clients to give them...

They have straight-up refused to discuss trying anything outside of Hyper-V and completely acted stupid when I mentioned something about moving the VHD that their software creates in Hyper-V and put it in our hypervisor directly... Said that's unsupported and we will not assist you.

Still trying to figure out how to get around this... I had Hyper-V running on a Proxmox VM but the software seems to stall out and never finish installing. I'm trying XCP-NG 8.2 but based on all the conversations here, I'm assuming Hyper-V will refuse to run.

@planedrop Exactly! Otherwise I didn't care because like you said, what the VM sees doesn't exactly matter in this regard because the host has ECC memory.

@planedrop Yeah Appreciated! I'm going to do a conference call with the vendor next week hopefully... They won't talk with me since I'm an MSP for my client... Stupid...

I'm experimenting with Nested virtualization with Proxmox... The application is installing but throwing errors, but I don't know if that's because of it being nested or if it's just throwing errors...

Regardless I may try XCP-NG 8.2 latest and see how it reacts with nested virtualization and just stick with that if it works... It'll be easier to backwards migrate everything from 8.3 to 8.2 than moving to Proxmox (I think?)

@AlexanderK Right, which in some ways in similar in what I'm needing, because there are applications that need Hyper-V.