Thank you!
No, partly because the QtSettings are a bit scattered and I wasn't shure which ones would be correct.
Removing and reinstalling QtCreator from Ubuntu repos didn't work, but removing and installing it via the QtUnified online installer did. Was hoping to avoid that because I didn't want to log in with an account but gave up eventually. I may try to switch back with cleaned settings at one point, but for now I'm just glad it works again.