> Video upscaling is probably going to be linear interpolation

This is probably true of the technology that's currently in the courtroom, but not for much longer, e.g.[1]. Apple have even done research on this[2], although I can't find anything that says it's currently in use on the iPhone/iPad.

[1] https://www.tvtechnology.com/news/the-secret-behind-8k-upsca...

[2] https://machinelearning.apple.com/research/gan