Luis Sequeira1 said in his post that he thought it was a third party app causing the problem, at least for some people. That's why I looked at login apps and background apps. I tried turning off a few different apps and restarting my Mac, but none made any difference, until I turned off the Adobe apps. Then spotlight was working perfectly.
Maybe for other people it’s another app that’s causing the problem.
The problem seems to vary. Some people have solved it by rebuilding the index, some solved it by turning off Apple Watch Login, for me it was Adobe running in the background.
Over the past week or so I’ve restarted my Mac many times as I’ve rebuilt the index (several times), turned off my Apple Watch login, and I’ve even reinstalled OS 26. But none of that worked for me.
If you’ve tried various things with no success, I think it’s worth looking at your login apps and background apps one by one to see if any of them are preventing Spotlight working.