Spotlight Search: Show ALL FILES, and exclude ALL FOLDERS

Solution 1:

You can set up some quite complex searches using Cmd ⌘ F in the Finder, rather than invoking Spotlight itself.

You can define many criteria & even save as a smart search for future use.

If you really want to get in-depth, you can use Spotlight's own query language, though the mechanics of that are well beyond my pay-grade.
I'll let Macworld - macOS: How to use Spotlight’s query language to create an All My Files-like feature - explain in detail.

Solution 2:

The Spotlight query you need to use the "kind" attribute. The search term you want is:

"search term" NOT kind:folder

For example, I tested this looking for an eBook titled Mastering OpenVPN. Here are the results of the two searches:

Kind Keywords for Spotlight Search

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