With GStreamer you can build a pipeline you like, you don't need to use RDP, you can send uncompressed frames plain over network like in the video. I'm not an expert on graphics processing. SLI or NVLink are (I think) proprietary parallel processing interconnects. But NVidia didn't invent parallel processing. I'm sure there are other solutions available. Though, I somehow doubt those will help you because they're generally tailored to other (HPC/datacenter/simulation) purposes and not for gaming. And I think they use something like Infiniband for that and not thunderbolt.

With the speed, mind the first article is 5 years old. And I'm not sure how the hardware in the second one compares to what Linus uses or if it's even the same generation of Thunderbolt. It's probably gotten way faster since. I can't try because only 1 device I own supports thunderbolt at all.

I think transferring files over thunderbolt networking or low latency video is nothing new. It can be easily replicated. And setting up 2 gstreamer pipelines is just two (lengthy) commands. Replicating NVlink is another thing, though. We probably need an expert on graphics drivers to tell if that already exists or how difficult that would be to implement. Most people will probably just fit 2 graphics cards into one computer or buy one faster GPU because that is both cheaper and way faster than connecting them in 2 separate computers with added latency.

(MPI would be an example of an open standard to do parallel computing with arbitrary interconnects.)