All Finder searches yield zero results. I suspect it's because "Shared" is in every search criteria.

Shared shows on my 10.13.6 installs.

How to rebuild the Spotlight index on your Mac

If searching your Mac doesn’t return expected results, rebuilding the Spotlight index might help.

1. Choose Apple menu () > System Preferences, then click Spotlight.
2. Click the Privacy tab.
3. Drag the folder or disk that you want to index again to the list of locations that Spotlight is prevented from searching. Or click the Add (+) button and select the folder or disk to add.
4. To add an item to the Privacy tab, you must have ownership permissions for that item. To learn about permissions, choose Help from the Finder menu bar, then search for “permissions.”
5. From the same list of locations, select the folder or disk that you just added. Then click the Remove (–) button to remove it from the list.
6. Quit System Preferences. Spotlight will reindex the contents of the folder or disk.

Manually Rebuilding Spotlight via Terminal

If the aforementioned Spotlight control panel approach doesn’t spur a reindexation of the drive, you may need to initiate it manually through the command line. Open Terminal and use the following command string to do so:

sudo mdutil -E /

This basically asks for temporary super user status, which is why Terminal may ask you for your password (it may not if you’ve used a sudo command recently or are already logged in as a super user or root. The command asks the unix tool mdutil to reindex the spotlight database for everything on the computer, including external drives, mounted disk images, etc. To re-index only for a specific drive, use the /Volumes path. For example, for an external drive named “MiniMe,” the command would look like this:

sudo mdutil -i on /

Rebuilding a drive index can take a long time, so be prepared to wait whether you do it through the System Preference panel or the command line.

In my Finder Preferences, I have two things set, with the latter having substantial impact on what you see in the Search panel.

1. General
   1. New Finder windows show: 🏠 Yourname
2. Advanced
   1. When performing a search: Search the Current Folder

With those settings, the items shown in the Search toolbar will be: This Mac "X", where "X" is the current folder name where you started the search. There will be no Shared folder item present.

Finder searches using the interface that you have shown depend on certain properties appearing in the first selector (kind), or adding them from the Other… menu item on that Kind menu. It also depends on how these are compounded to form the overall search criteria. I do not use this form of search in the Finder, preferring Spotlight queries in the normal Finder window search field, or Spotlight itself. These are explained and demonstrated in the Narrow your search results on Mac content.

Thanks, this the link we needed for others wishing to help...

https://pastebin.com/X6hSrgt6

Delete these 2 Adware files,,,

1. /Library/LaunchAgents/com.genieo.engine.plist
2. /Applications/Genieo.app/Contents/MacOS/Genieo

o1dbrowserplugin is a fake old Internet Plug-in.

Restart.

The other item I did not mention in the Finder Preferences was:

1. Sidebar
   1. ☑︎ 🏠 username

When you click that in your Finder Favorites Sidebar, it takes you to your home folder, if you happen to be elsewhere.

You do not need to select your startup (e.g. Macintosh HD, etc.) drive name prior to a search. That may pickup the Shared folder as it is included in MacIntosh HD folders. I never select the startup drive prior to any Finder search, and that may be contributing to your picking up the Shared folder location which is part of the MacIntosh HD contents.

Just start in your home directory, or a specific folder, and if nothing is found, then click the "This Mac" alternative which represents your search applied to the entire Mac outside of your current search location.

Neither High Sierra, Mojave, nor Catalina will show that Shared folder in the Search toolbar. At least, in my implementations of these operating systems. They also do not offer All My Files in the Favorites sidebar. OS X El Capitan does show the Shared folder in the Search toolbar, even with the same Finder Preferences settings as on my newer macOS releases, and does offer All My Files in the Favorites collection. I always disabled All My Files in the Finder Preferences : Sidebar.

I would simply ignore the Shared folder when it appears, as there is nothing in there of interest to you anyway.

Eject that Flash Player installer from your Desktop if you have not done so already.

Exactly like mine, though I did uncheck Spotlight Suggestions in categories, and unchecked Allow Spotlight Suggestions in Look up (due to clutter) on the Spotlight panel below categories.