Reddit reviews StarTech.com 50 ft DisplayPort Cable with Latches - Active - 2560 × 1600 - DPCP & HDCP - Male to Male DP Video Monitor Cable (DISPL15MA)

I'm planning similar stuff (NAS + Gaming VM server in one, with lots of ECC due to the NAS; powered up on demand via my RPi/WoL). I tried around with my current machine, and this are my results regarding your second point:

1. Steam Remote Play works nice with my Steam Link in the living room, connected via Gigabit to my PC
   
2. Parsec (https://parsecgaming.com/) worked nice streaming to my Linux Laptop when I was visiting friends, at least the quick test with Factorio was great (but obviously I couldn't join LAN games, though some OpenVPN-magic might solve that). I'm on a 400/50MBit line.
   
3. For non-gaming use, RDP could still be an option (or just ssh if you're on Linux)
   
   Obviously you need some hardware where you plan to stream to, but you only need a good connection (e.g. decent WiFi or Ethernet). Regarding using DP cables, that's pretty limited as per https://superuser.com/questions/451126/mini-displayport-cable-max-length#451128 A 50ft active display port cable is 80US$: https://www.amazon.com/StarTech-com-50ft-15m-DisplayPort-Cable/dp/B00EG3YA2G There are similar products for USB - you just need to pass-through one of your MoBo's USB hubs.
   
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   The nice thing about the software solution: Either one is free, so you can basically try them out right now with you existing hardware.
   
   Yes, you already said you don't want it, but have you actually tried it? Personally, I wouldn't tear open my walls just for these cables (especially since there is imminent danger you abandon it and go the easier "just boot windows on my gaming machine" route). Okay, maybe you have "empty conduits" (is that the word?), then that's mood ;-)
   
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   With your other points:
   
   
4. As an avid Linux user, I'd say easy: https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF Notice that shutting down the gaming VM could require you to power cycle your GPU (and thus the server)
   
5. See wall of text above
   
6. One GPU per VM, unless money isn't an issue at all (in that case get some IT consultant to built it for you)
   
7. Depends; as others pointed out, if you want GPU accelerated stuff (e.g. video de/-encoding, hardware accelerated rendering in chrome,...) then yes, one GPU per VM with that requirement
   
8. You're going to quickly exhaust your available PCIe lanes: Ryzen 3xxx has 24x PCIe lanes, take 16x for the GPU, 4x for a NVMe disk, you still have 4x to spare (unless the MoBo needs those for peripherals, I don't know). If these last 4 are available, your 2x10GbE will probably use them. With a bit of bad luck, your BIOS will throttle your GPU to 8x in that case (which I personally wouldn't mind for pure gaming loads), since it only sees "two slots in use", depends on how dumb it is. Add a second GPU and things get crowded on that bus for sure (2*GPU + NVMe + NIC = 2*8 + 4 + 4 = 24). Adding a SAS controller or second NIC (you mention more 1GbE ports) will be difficult then. I am not sure if there are MoBos with PCIe switches for more lanes/slots, but that would solve that problem (assuming you will basically never see 100% load on the PCIe bus during real world use) - drawback here is: Last time I checked PCIe 2.0 switch ICs were pretty expensive, and I don't believe they became cheaper. Just for comparison: The "old" Threadripper 2920X has 64 PCIe 3.0 lanes, so there it just boils down whether the MoBo offers enough PCIe slots or not.
   
9. Be prepared to simplify the whole sh*t down again, and end up with the same setup as now, just with different hardware.

Could this active cable solve your issue? https://www.amazon.com/StarTech-com-DISPL15MA-Active-Displayport-Cable/dp/B00EG3YA2G?th=1

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or this one?

https://www.amazon.com/Club3D-CAC-1069-DisplayPort-Cable-Certified/dp/B07DKPBWB3

I was looking at cables like this active 50ft cable, But maybe they won't work well for VR. I don't know.

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https://www.amazon.com/DisplayPort-Cable-50-15m-Active/dp/B00EG3YA2G/ref=sr_1_3?keywords=50ft+active+display+port&qid=1558195183&s=gateway&sr=8-3-spell

I'll have to double check this, but I think they make active display port cables that can go longer.

Edit: there are in fact active display port cables like this one that can go up to 33 meters. That one is only 15ft but apparently active cables can go up to 33 meters.

StarTech.com DisplayPort Cable -... https://www.amazon.com/dp/B00EG3YA2G?ref=ppx_pop_mob_ap_share

This one did not work for me, just a heads up. Let me know if you find a working one!

I found these products wich could help to deploy Oculus Rift S in several rooms .

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DP Amplifier : https://www.amazon.com/LINDY-DisplayPort-1-2-Extender-Repeater/dp/B01BOS08XK/ref=sr_1_14?keywords=Lindy+Extender&qid=1557218913&s=gateway&sr=8-14

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DP Coupler F/F : https://www.amazon.com/LINDY-Female-Display-Coupler-41020/dp/B0037LNXW6/ref=sr_1_fkmrnull_1?keywords=Lindy+41020&qid=1557219083&s=gateway&sr=8-1-fkmrnull

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DP Cable 15 m : https://www.amazon.com/DisplayPort-Cable-50-15m-Active/dp/B00EG3YA2G/ref=sxbs_sxwds-stvp?crid=9LZL5HC621I3&keywords=lindy+displayport&pd_rd_i=B00EG3YA2G&pd_rd_r=d7a45e00-abdb-4243-9be4-e34f748b70ff&pd_rd_w=9KdSu&pd_rd_wg=U1N5d&pf_rd_p=a6d018ad-f20b-46c9-8920-433972c7d9b7&pf_rd_r=ZYW420EDG5ENCVPPNV8V&qid=1557219161&s=gateway&sprefix=Lindy+display%2Caps%2C209

https://www.amazon.com/DisplayPort-Cable-50-15m-Active/dp/B00EG3YA2G

IIRC, the max length for DP is 3 meters. Going 10 meters would likely require some sort of active cable like this


I certainly wouldn't recommend it.

You can also check out www.displayport.org for a database of certified cables, which are recommended when high bandwidth is required (especially for adaptive sync)