2023 October 4 Edit:
After some digging around the Discord, I saw that Vortex (the developer) commented that SOTS does not currently support special world seeds (as of 2023 September 22).

"SOTS requires the structures to play so just don't play with the mod if you plan on using a seed. I may try to add seed compatability eventually but right now it is not a plan of mine"

Given how the information is spread out, I think updating this comment is more appropriate than deleting it. I'll try to update this discussion as appropriate

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OLD COMMENT

I tried generating a couple of worlds using "GetFixedBoi" as a world seed, and eventually I tried it with "DontDigUp". In both cases, it didn't appear that the world generated: tModLoader didn't throw an error and it appeared to continue generating the world, but after a good 30 minutes I stopped the process (worldgen on a random seed takes no more than 5 minutes).

From attempting to generate a "DontDigUp" world, the worldgen process appears to be stuck on the "Generating Sky Artifacts" step. Hope this helps, let me know if there was any other information you might need