Dear Maintainer,

I have a custom URL filter setup via a .desktop file in
~/.local/share/applications and the other XDG/Gnome MIME associations
methods.  When apps are firejailed, they ignore that custom mapping
and default to a new, uninitialized Firefox instance, even if Firefox
(jailed) is already running.  As far as I can tell, the user-local
MIME/desktop files are already whitelisted, but yet this problem
exists.

Here are two examples of this setup:
* https://github.com/nbeaver/thunderlink-install-guide
* https://gitlab.com/atorat/url-filter