So if I have scarab installed but I disabled all of my mods, do I still need to uninstall scarab for my run to not be rejected?

At the bottom left of scarab there should be a 'Disable API' button. As long as the API is disabled and you cannot see any mods nor the modding API text at the top of your screen in the menu, then your run will be valid!

ok thank you very much!

When I launch Scarab, I get only a gray screen, without mods. Does anyone know how to solve this problem?

If you move the window, there's something that say your installer is out of date. Just click OK, or Update

After pressing OK, nothing happens, the same gray screen

OK, I downloaded a newer version of Scarab, now it gives the error "Unable to fetch modlinks, the operation timed out"

I can't help with tat.