Apple Mail can't find new messages, smart mailboxes don't work, Spotlight rebuilds changes nada

OK, so turns out I had a buildup of false volumes in "/Volumes" This is something macOS sometimes do when it can't get to a mounted volume, it creates a new fake one, then fails to handle this. This happens very seldom though. It's the first time this affects the internal drive.

After I had deleted the false volumes, carefully ejecting external disks first and making sure the internal was the internal and not the false one, I proceeded with deleting the Spotlight index in Terminal:

sudo mdutil -E /

Then I removed my internal drive from the Spotlight prevention list in System Preferences and four hours later my complete Spotlight index have been rebuilt. Had to turn off Virus scanning as it was interfering with file access and taking up valuable CPU time.

Likely I got partial results as the false internal drive had a partial index also when I had prevented the internal disk. Fixed. I really gonna need that index the coming days.