Well, things won’t import as virtual textures. I had some messed up numbering that start at 1010, and that imported as a (badly arranged) virtual texture. But when all of the numbers are correct and start at 1001 it just imports the one image. Kind of annoying.
I’ve poured through the small amount of code that handles this and it seems fine, so I don’t know what’s up.
Edit: I just figured it out. The base names before the UDIM ID all have to be the same.