Shows contents of root folder in devices panel of File Manager editor

[thelabcat]

From https://developer.blender.org/T99894

System Information
Operating system: KDE Neon, Fedora, Linux Mint
Graphics card: NVidia GeForce 2060 RTX SUPER

Blender Version
Broken: 3.2.1 and all 3 versions

Short description of error
When in the File Manager editor on the Flatpak version of Blender, the devices panel does not just show connected storage mediums, but rather only mounted mediums, plus all folders in the system root folder.

Exact steps for others to reproduce the error

• Install blender via Flatpak, and run.
• Go to File -> Open.
• Observe the device panel in the top left corner of the File Manager editor. It will show things like usr, home, etc.

Expected behavior
Like all other packaging and executable formats, Blender hopefully would show only mounted devices, but one of these would be the system root drive. This may not be possible with Flatpak, at least not without additional privileges of some kind. It is, however, possible with the AppImage and the official Blender Snap.