To connect my windows desktop to lg ultrafine - I use a bidirectional display port to thunderbolt 3 cable (amazon basics)

Wow! Didn't know those cables can go the other direction as well. That's huge!

Thank you! Another example that writing something wrong on the internet is the best way to find the truth :)

That said, it looks like there's just one input port and three output ports. Would need to do some hack there as well, to avoid constant cable changing.

Several Intel and AMD motherboards have both Thunderbolt ports along with a DisplayPort in port that lets you pipe the output of a discrete GPU (like an RTX 3080) through the Thunderbolt connection. These will probably work just fine with the Studio display. Some PC laptops with Thunderbolt and more capable GPUs probably work with it too.

There are bidirectional DisplayPort <-> USB-C cables, as well as DisplayPort+USB-A -> USB-C cables/adapters that work with the XDR display at 6k, or there are PCIe cards that add a USB-C port with DisplayPort alt-mode support

Only problem is that you'll probably need to extract a BootCamp driver to control brightness/volume, assuming one will exist for this monitor.

(well, if it supports HDR input, you'd use Window's SDR brightness to control it that way instead)

Amazingly, NVidia cards had this port on previous generation models, but it got removed for some reason. (Though it's actually not clear to me it would work; they did some non-standard stuff to get USB 3.1 instead of USB 2.0 alongside DisplayPort lanes.)

It most likely wouldn't work with a Windows PC anyways due to the tight macOS integration anyways; my iMac in Boot Camp can't use any of the USB-C ports on a connected LG Ultrafine 5k at all.