All of the 90s Star Trek series were filmed on 35mm, but all of the post-production work (editing, SFX, etc) were done on tape, at 480p. There's no 35mm copy of the final result to scan and color-grade for a "normal" HD remaster. For the TNG remaster, what they actually did was re-do all of the post-production from the original 35mm negatives. VFX were re-composed, some were re-done in CG. They finished the TNG remaster just as streaming services were ramping up and Blu-Ray disk sales declining, and sales were disappointing given the amount of work that had to go into them.

Paramount will never remaster DS9 or VOY because they don't expect to make the money back, because neither was as popular as TNG. And it's worse for DS9 and VOY because they extensively used CGI effects for things like ship battles, which were originally rendered at 480p. If the original assets could be found, they could be re-rendered, but in many cases, they would have to be fully re-created.

Fans have created AI upscales which are generally better than watching the horrible 480p releases that were on Netflix and are now on Paramount+. But they are also sometimes uncannily smooth and unpleasant.

Ugh no thanks, AI upscales are exactly what I don't want and not something that should be mentioned in the context of fan projects like the 1977 star wars restoration which take great care to restore the original content instead of hallucinating higher resolutions.

My main problem is that the publicly available non-streaming releases are NOT 480p but 480i (actually even worse than that, partially interlaced and partially telecined) with horrible compression artifacts. With access to the production masters you could surely produce a better release than that.

Your "never" is also a needlessly strong word - people would also have said TOS and TNG remasters would "never" happen before they did. Also keep in mind that just because a company says something is not profitable it doesn't mean that they wouldn't make the money back - it could also mean that they just wouldn't make as much profit as they would doing something else. That means that even small changes to the equation or just someone pushing for it hard enough can sometimes tip the scales. Blu-ray sales declining are also not really an argument as streaming services didn't kill production of new series either. But we were also lucky that the trek remasters we got were faithful to the originals which is not guaranteed to be the case so maybe we are better off without more remasters in the current climate.

Is there a name that these upscaled releases fall under to easily find them?

Star Trek in particular (I was watching voyager yesterday) the quality is always pretty depressing when shown on a larger TV. Been recently thinking about trying to find the best quality I can find but it is always a lot of trial and error. But if there is a common name and tag I could look for that would be great.