However, I am looking for ways to remedy this problem. I’m curious about buying 4K downloads of the prequels (or 1080p, at least)
I recommend you use Schormann’s preservation of TPM as a base for your edit. It’s in 1080p, it’s equivalent to the DVDs changes-wise, and looks way better than either the 2011 HD Blu Ray or the 2020 4K Blu Ray.
I really disagree. It may not be as DNRed but it’s overly cropped, noisy and has really bad edge enhancement. The 4K release is the best this movie has looked short of someone scanning an original theatrical print.