I have hundreds of images that weren't able to build a smart preview since the drive that was containing my Lightroom smart previews ran out of space. I would like to know how to find those images that don't have a smart preview. How can I do so? Thanks!
You can find photos without a smart preview by using a smart collection.
Go to Library → New Smart Collection... and add a condition Has Smart Preview is false:
This gets you the photos that do not have a smart preview.
Then you can follow the steps from the manual to create smart previews on the fly.