In mount
system command's output in Debian Linux 10-like OS I have following string:
portal on /run/user/1000/doc type fuse.portal (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)
What means this string?
It seems that it's used by flatpak and gnome/gtk and kde/qt for desktop applications isolation. See: https://docs.flatpak.org/en/latest/sandbox-permissions.html#portals