After months of using Ubuntu 22.04 as my main OS, and not being able to view thumbnail images when choosing which to files to upload online, I have finally arrived at a solution - Ubuntu 23.10 running GNOME 45.
There is a trick to this, however. In order to have thumbnails present, you must first enter the directory with Ubuntu's file manager, Nautilus. Only then will thumbnails be visible. To demonstrate this, here is what things will look like if you have not visited a directory with the file manager yet,
And after visiting the directory,
I wouldn't call this perfection, but I am so much happier with this. Thank you to everyone involved in this update!