I have no answers for you but find this project fascinating and would love it if you documented (photo/video) some of this journey 😀

I'd be interested as well, since the assisted suicide of VMWare by Broadcom I have a desire to rip out ESXi from my home lab server and replace with something else.

Proxmox seems like the best all in one.

Bought some parts so we'll see how this goes. If it works I'll have to decide if I buy a case per GPU or replace the GPU. For longevity thinking a case per.

If I have the 7900xtx as a egpu for 10+, 980ti internal for XP, Vista and 3060 for 7-8 on this 5950x then that's pretty good.
If I wanted I could do another case for 1080ti for Vista (waste of money for another case.....) or a 3080 case and remove the 3060 and replace it was a Geforce FX 5200 for <= 2000 but I'd need to see if I have a PCIe slot for an Audigy otherwise I'll just have an X-FI for XP and onboard audio for everything else.

I don't want my i7 6700k to go to waste so I'm fine with it being a <= 2000 machine with XP+ as backup with a 780GTX for now.

If there is any interest then I'll post parts and pics once I have it working.

Tested 980ti and X-Fi in 5950x machine which work well.
Took the 3060 out of the 5950x machine for the oculink card when I get it.
Replaced the 980ti in the i7 machine with a 3080. This will be swapped out with the 780GTX when/if I make the 3080 a egpu depending on how well the 7900xtx egpu goes.

Current machines:

PROXMOX TEST XP/Vista/7/8/10/11/Linux

CPU: Ryzen 9 5950x
CPU Cooler: Corsair iCUE H150i w/ 3x Noctua NF-A12x25 PWM chromax
Motherboard: MSI Meg X570 Unify
NIC: Intel Ethernet Converged Network Adapter X550-T2 (10GB)
Memory: G.Skill 32GB DDR4 PC4-28800 3600MHz Ripjaws V for Intel CL16 (16-19-19-39) Dual Channel kit (2x16GB)
EGPU: SAPPHIRE NITRO Radeon RX 7900 XTX 24GB GDDR6 PCI Express 4.0 x16 ATX Video Card 11322-01-40G (Windows 10/Linux+)
GPU: Video: Zotac Geforce GTX 980 Ti 6GB AMP! Extreme GDDR5 ZT-90507-10B PCIe (2000/BWC,Windows XP+)
Video card: EGPV-1101-C1 M.2 (Proxmox Console)
Audio: Realtek® ALC1220 (Vista+)
Audio: Sound Blaster X-Fi Titanium (XP)
Monitor 1: Acer XB271HU 27" 2560x1440 "Acer Predator XB1"
DVD: Blu-ray LG WH16NS60
SSD: Seagate FireCuda 530 1TB
SSD: Seagate FireCuda 530 4TB
PSU: CORSAIR RMx Series, RM1000x, 1000 Watt, 80+ Gold Certified, Fully Modular Power Supply
Case: Corsair 600C Black ATX Full Tower Computer Case w/ 3x Noctua NF-A14 PWM chromax

PROXMOX Test DOS\9x (VESA)/NT4 (VESA)/2000 (XP+ Backup)

Processor: Intel Core i7 6700k
CPU Cooler: Noctua NH-U9S w/2 Noctua A9 92mm fans
Motherboard: ASUS PRIME Z270-A
Memory: Patriot Viper 4 32GB (4 x 8GB)
NIC: Intel X540-T1 10GB
SSD: Seagate Firecuda 530 1TB (Proxmox)
SSD: Seagate Firecuda 530 2TB (Proxmox VMs)
PSU: Corsair RM850x
Audio: Creative Sound Blaster Audigy PCIe RX 7.1 (9x/2000/XP)
Monitor: Dell Ultrasharp U2410F 24" 1920x1200
GPU: GIGABYTE Gaming OC GeForce RTX 3080 10GB GDDR6X PCI Express 4.0 ATX Video Card GV-N3080GAMING OC-10GD (rev. 2.0) (7+)
GPU: 880GT 512MB (2000 Vanilla)
GPU: Geforce FX 5200 128mb (9x-NT) (2k-xp for games that need it)
Case: CoolerMaster ATC-110 w/ 4x Noctua NF-A8 PWM fans
Amebay 5.25 Inch Front Panel USB Hub 2port 3.0, USB 2.0 for Computer Case
DVD: Blu-ray LG UH12LS28

Got the egpu built, just waiting on the oculink card. If it works then pics if it doesn't then mabye pics. heh.

Got the final part today but found out during testing that the 7900 xtx is incompatible so swapped it for a 3080. Verified that passthru works via proxmox, installed the drivers, verified pcie 4.0 x4 and loaded cyberpunk. Won't be able to test more until after the weekend.

DLSS quality at 1440p was 38fps which I think is pretty good but would need to check reviews. All I need is good enough for mostly testing and sometimes playing so should be good.