There is a massive gap between the capabilities of the two, once you get past the simple edits. The same can be accomplished by hand in both, but it’ll take much longer and parts will have to be done by hand.

I’m not sure how much of it is AI assistance. Affinity is cheap enough and good enough I don’t deal with GIMP for anything complex.

I think darktable (which is FOSS) is more what he’s looking for since he’s using Lightroom.