Hi @Pstork1 - first of all let me apologize for being so short/curt yesterday, it wasn't directed at you or your solution, just frustration in general that a seemingly simple task was taking so long. (And I will blame lack of sleep also.) And thank you for your replies!
So, for "Get File Content Using Path" - both of the Dynamic Content options returned by "For A Selected File" result in 404. The itemURL returns a URL and not a path. And the fileName, as you point out, doesn't have the path either. So it seems that we need "Get File Properties" to obtain the full path to pass to "Get File Content Using Path" - which is fine, just unclear (and not intuitive.. I think that's part of why I was stumped.)

Now, moving on to "Get File Content" -- I think this is where I got really frustrated with the documentation. The "For A Selected File" Action returns Dynamic Content called "ID" which is defined as "File Identifier". So, I believe that it is reasonable for the user to assume that this Dynamic Content is the required input for "Get File Content" - as shown here:

As for documentation, yes, you do correctly point out that the entry for "Get File Properties" notes that its "Identifier" Dynamic Content can be used with Action "Get File Content". In fact, that's how I figured out to add in the "Get File Properties" Action to get my Flow working. But nowhere in the "Get File Content" Action documentation does it say anything about requiring the "Get File Properties" Action in order to obtain the File Identifier input that "Get File Content" is really looking for.

So, when troubleshooting, I don't think folks would think to look at "Get File Properties" as a first resort, thinking to themselves "Well the 'For A Selected File' Action is already returning 'File Identifier' so I'm not looking for additional properties to fix this 404."
Anyway, not that my opinion matters to MS, but I think that the file identifier term should be subdivided to be more granular - e.g., the "For A Selected File" Action output of ID (the Integer ID) should have a more specific, contextual definition, perhaps something like "Library File Identifier" to denote that it's the identifier within the Document Library.
Anyway, thanks again for the replies. Hopefully this thread helps out some other users in the future - cheers! 👍