Failed to load mods: error while running setup for prototype "upgrade-flat-kr-advanced-solar-panel" (recipe): recipe is in 'crafting' category but has a non-item ingredient 'nitric-acid'

This might involve modified recipes from SE or 248k or others, but either way the error type seems pretty clear to me

That sounds like krastorio, right? Did this just start happening from my update earlier today, or are you just trying to add Flat Solar for the first time?

Adding flat solar for the first time. I first saw the error yesterday just before your latest update but was a little bit late reporting it

And yes krastorio. Also space exploration and 248k which have a significant amount of recipe modification and integration in case you have trouble reproducing the bug.

Actually, I just found the issue and uploaded a fix for it.

Actually, I just tested it with krastorio 2 and flat solar by themselves, still crashes with the same error

^not sure if you missed it, but see my previous response.

Yup just tested it, looks good!

Some minor weirdness with upgrade path recepies with the mess of mods I have as to which previous solar panels to use in an upgrade (i.e. Upgrade from flat or not) but it's such a small detail for a custom niche mod pack that I don't think it's worth bothering with trying to polish it. It all looks perfectly playable as-is.

Yeah, upgrade path is tricky with all of the different mods, and each having their own upgrade path. I do standardize the replace groups, so those at least work. At some point I've been meaning to go through and regenerate upgrade paths for all flat and standard panels based on power generation.