Reindex or rebuild spotlight in MacOSX Tahoe

Test if spotlight is enabled:

√ ~ % mdutil -sa
/:
Indexing enabled. 
/System/Volumes/Data:
Indexing enabled. 
/System/Volumes/Preboot:
Indexing enabled. 

If it is disabled rather than enabled, the first solution is to try to enable it:

1- In the Terminal, type and run the command: sudo -i.
2- Enter your administrator password and press Return.
3- Continue to run the commands mdutil -Ea and mdutil -ai off.
4- Enter the command mdutil -ai on and press Return, and you will see a message saying that indexing is enabled.

Second solution if the first one does not work:

sudo mdutil -ai off
sudo pkill -f mds
sudo pkill -f mdworker
sudo rm -rf /System/Volumes/Data/.Spotlight-V100
sudo rm -rf /.Spotlight-V100
Restart the Mac - This step is crucial
After reboot, enter in terminal :
sudo mdutil -ai on
Force a complete reindexation :
sudo mdutil -E /
sudo mdutil -E /System/Volumes/Data
Test if it works :
mdfind "kMDItemContentType == 'com.apple.application-bundle'" | head -5

Indexing takes a few hours to finish completely, but you’ll see the apps and recent files right away.

Based on 

https://www.reddit.com/r/MacOSBeta/comments/1mob0co/solved_macos_tahoe_public_beta_1_spotlight/?tl=fr