Apple - Spotlight borked after macOS Sierra update

Did you reboot after #4 above? I think that should work... If not this may help:

sudo touch /.metadata-never-index

Reboot...

sudo rm /.Spotlight-V100/VolumeConfiguration.plist
sudo rm /.metadata-never-index

And reboot again. You can try this for every volume.

See also: http://www.filetypehelp.com/purpose-files-metadataneverindex-file-extension/

After leaving my Mac alone for the weekend, my fears were confirmed and there was never any change to this Spotlight issue. Given the other threads here and elsewhere, it appears that Sierra has some challenges when doing an in-place upgrade.

Resolution:

1. Confirm you are fully backed up (multiple backups preferred). THIS IS THE MOST IMPORTANT STEP!
2. Reboot into Recovery Mode (hold down Command-R while Mac begins to boot).
3. Open "Disk Utility" and erase the macOS partition (You did confirm those backup(s), right?).
4. Once HD is erased, exit out of "Disk Utility", open "Install macOS Sierra" and install Sierra from scratch.
5. After install completes, restore from backup.
6. Get back to your life. ;-)