After doing a fresh install of Ubuntu 22.04, then installing Okular as a snap from the App Center, the icons in Nautilus for each of my pdf files are in the form of the first page of the pdf file, and not the icon for the Okular program (which, by the way, is awful in the Snap version). I want all my pdf files in Nautilus to have the same icon appearance, preferably something that is distinctly “pdf-ish.”