I battled this issue for over two weeks and was able to solve yesterday -- hopefully this would help others. It boiled down to finding the right USB 3.0 add-on card: PCIE USB 3.0 Card, ELUTENG 4 Ports PCI Expree to USB Expansion Card (https://www.amazon.com/gp/product/B07W82SV3V/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1)
My motherboard is relatively old (Asus Rampage IV Extreme) and while it has on-board USB 3.0 ports, none of them worked with Reverb G2. I've experimented with various versions of the drivers, several add-on cards (with MOLEX or SATA power connectors), external powered USB 3 hubs -- and was getting really frustrated. However I've seen this specific card mentioned on Reverb G2 user forum, and decided to give it a try. It just worked! As the bonus, this card does not require an additional power connector and draws all the power it needs from the PCIe slot. In fact I have it plugged into the older PCIe 2.0 1x slot on my RIVE, and it works just fine! Windows 10 Pro installed the drivers automatically, detected the Reverb G2 plugged into it, and everything was a smooth sailing from there. Hope this helps!
I do like the XT1. The only issue I ran into was setting up, but a big of googling and I found out the steps that I wrote in the first message. Firmware is key, I think it shipped with 1.04, and I had to update it to 1.07, or something similar.
After that, when I upgraded to an ASUS x570 mobo, it just flat out wouldn't work. I dove deep on google searches for that, and actually found a forum buried somewhere with a thread about the exact same issue. I ended up buying a $15 USB PCI card and that solved it. I don't know if they've fixed the issue with BIOS updates or not. Here's a link to that card on Amazon, but there are plenty that should do the trick: