Solved! Go to Solution.
This can be solved by using either the "My Files" app on the mobile device or using your device hooked to a PC.
Found this info from a guy named Mike Dwyer1:
Look in the folder called "DCIM".
Tag/check all the folders **EXCEPT THE CAMERA** folder and MOVE the folders to the PICTURES folder.
After you do that, go back into your Google Photos app and loo at your Device Folders to Sync area for the newly moved folders.
Hopefully they will now be available for you to upload/sync/backup.
This just worked on my fiance's S21 Ultra.
The fix below worked well, thanks! Move any folders (outside of Camera) from the DCIM to the Pictures folder.