And remember - there is no accurate cut in long-GOP structure files without re-encoding.
That’s why I downscale my input in Premiere (to fit within SeedVR2 constraints), export it in AppleProRes and then cut to frame-accurate segments in LoselessCut.
I didn’t quite understand; there’s no GOP structure without re-encoding? I’ve read threads that mention GOP, but I don’t know what it is. And the Apple ProRes codec isn’t uncompressed, so there must be some loss, right?
I think he means GOP-structure is to long he can’t do lossless cuts where he wants.
GOP - Group Of Pictures consists of, well pictures. Only several frames are truly independent from each other. They are called I-frames and true cut can be done at the I-frame only. Other frames are calculated from the previous frames - P-frames and from previous and next frames - B-frames.
These frames are not suitable for cutting. So, true cut can be done at the nearest to your desired timestamp I-frame.
There’s a good article explaining IPB frames: I, P, and B-frames - Differences and Use Cases Made Easy - OTTVerse
Speaking of ProRes - I know it’s not lossless, but for s low-quality input it doesn’t matter.
Ah yes, I understand more or less 
Indeed, if the source isn’t lossless, it doesn’t matter; ProRes already provides very good quality.
