I had this problem and the attached patch for xdg-settings worked for me (see my comment at https://gitlab.freedesktop.org/xdg/xdg-utils/-/merge_requests/52#note_1488548).
With this, the Firefox snap recognizes itself as the default browser for me (Kubuntu 22.04), whereas previously it would not.
I had this problem and the attached patch for xdg-settings worked for me (see my comment at https:/ /gitlab. freedesktop. org/xdg/ xdg-utils/ -/merge_ requests/ 52#note_ 1488548).
With this, the Firefox snap recognizes itself as the default browser for me (Kubuntu 22.04), whereas previously it would not.