searching for files in finder is not displaying all results / any results

Try reindexing Spotlight. Rebuild the Spotlight index on your Mac - Apple Support

For some, the GUI method doesn't work (especially in Tahoe).

In Terminal, copy/paste in this command. Enter your password when requested, but when you do, you won't see anything echoed on screen.

sudo mdutil -X /; sudo mdutil -i on /

It should respond with the number of files/directories removed and then "Indexing enabled."

Vici_65 wrote:

Select search in the finder window and type part of the filename. Before the Tahoe upgrade the window would show all files with the search phrase in the filename. Now the window is either blank or only one or two files are shown.

For an on-going issue there has been some relief—

From the Finder>Go>Go To Folder, copy & paste:

~/Library/Metadata/CoreSpotlight/ 

delete all files within the "CoreSpotlight" folder, reboot and compare your results .

ref: Tahoe: Spotlight Doesn't Index and Search… - Apple Community

Also, make sure that System Settings > Spotlight is set to show results from Documents and Folders.