It would be great if Firefox would ship appstream metainfo¹ so
Firefox can show up in "Software Centers" like gnome-software making
it (un)installable for users that don't want to resort to
the command line.

Since the appstream info ties to the desktop file it sounds
reasonable to ship that within the debian/ folder like the desktop
files. A merge request is at

https://salsa.debian.org/mozilla-team/firefox/-/merge_requests/5

I've filed this at severity whishlist since I don't think we mandate
the existence of appstream data anywhere within Debian yet.

Cheers and thanks for maintaining Firefox within Debian,
 -- Guido

1: https://www.freedesktop.org/software/appstream/docs/