It looks like the indexing of network drives in Monterey is not working properly.
All Search Results categories are checked in Spotlight settings and nothing is in the Privacy exclusion list. My system drive is indexed correctly and spotlight is working fine there. However, I have two network drives mounted on /volumes.
The indexing is enabled.
Prompt> mdutil -as /: Indexing enabled. /System/Volumes/Data: Indexing enabled. /Volumes/ludo: Indexing enabled. /Volumes/video: Indexing enabled.
Spotlight seems to do the indexing job as we can see the indexing progress bar when trying to do a search.
But no results (after indexing complete of course), and no .Spotlight-V100 folders on the external drives as well. I don't know if Spotlight still stores the indexing files there in Monterey (The folder isn't on the system drive either, where search is working fine).
So, is Monterey having an issue there? The exact same setup was working fine on another MBP and another OS version. Did anybody succeed in indexing external drives on Monterey?
I tried turning indexing off and on again with
sudo mdutil -i off /Volumes/Drive_to_index and
sudo mdutil -i on /Volumes/Drive_to_index, rebuilding the index with a
sudo mdutil -E /Volumes/Drive_to_index but no changes.
Following Rory's answer, there is no hidden
.metadata_never_index_unless_rootfs file on any of my external hard drives.