Firefox opens local PDFs with an inconsistent path
When a PDF saved locally is opened with Firefox, Firefox's address bar doesn't show the PDF's location, it shows an address in /run that appears to be some kind of temporary staging directory. Why can't Firefox just open PDFs from their actual location on the drive? Not sure if this is a Linux problem, but it does it fine on Windows. And I couldn't find this issue on Google. This is annoying because I have to specify the location of the PDF every time I restart the computer. It's a textbook that I plan to spend months reading.
Solution
This is normal behavior of flatpak, it's sandboxed. If you access this folder often you can whitelist it via Flatseal
