Well, the routes might manifest somewhere as files, but I don’t expect anyone to be able to viably parse them without commands like ip or ifconfig (or know where the files even are).
Some devices (like disks for example) are very straightforward to use as files, while some other special files (like USB devices) are so weird/ugly to use that everyone uses tools/libraries to access them (like libusb).
This is very off-topic, but there’s a great talk by Benno Rice that talks about this (among many others): youtu.be/9-IWMbJXoLM
They aren’t asking about changes to a file describing the routing config, rather the actual in-use routing config. Unless the routing rules are modified through a couple of files (which I doubt), this doesn’t answer the question.
I don’t know anything about how Firefox is packaged for snap, but snap’s “sandboxing” might interfere with getting all fonts.
You might want to try using Firefox without snap (which has some other benefits, especially around startup time) or adding ~/.local/share/fonts (which is where fonts are supposed to be installed for users) to some sort of allowlist.