The instructions for fixing a Mac's corrupted spotlight index are amazing. I was planning to do it earlier this year, but the number of manual actions was just too ridiculous. Then, after it was broken for months, it spontaneously started working again.

It's a little heterodox, but not hard at all[1] and it takes literally less than a minute to trigger the rebuilding.

[1] https://support.apple.com/en-us/102321