Find images without keywords

You can also use the Filter Bar as shown below. This allows selecting specific folders in the Navigator and/or by Date, Camera, Lens, etc. using the 'Metadata' filter along with the 'Text' filter. This may be helpful for finding images that should have common keywords, such as from a specific trip or assignment (i.e. date).

Actually all you have to do is create A New Smart Collection, set it to Keywords and then Are Empty. That will show all images that do Not have a keyword (or keywords) assign to them.

Name it something you can remember, like Without Keywords, and click the Create Button.

You could also create a Collection Set, call it Smart Collections, and place all current Smart Collections in that Collection Set and then place all future Smart Collections in that same Collection Set. That way you can Collapse it when not needed and keep the Smart Collection in one place and away from your regular, Non Smart, collections.

Create a Smart Collection with:
Other metadata -> Keywords and select "are empty"

Search for images where Keyword does not contain a e i o u y

That should find most or all of the desired photos.