Comment 5 for bug 1970248

The defaults.list handling is still valid,
https://gitlab.gnome.org/GNOME/glib/-/blob/main/gio/gdesktopappinfo.c#L985

The issue is that it ranks lower than gnome-mimeapps.list which got install by error since a gnome-session merge this cycle
http://launchpadlibrarian.net/569661464/gnome-session_40.1.1-1ubuntu1_40.1.1-3ubuntu1.diff.gz

the
>- don't install gnome-mimeapps.list (installed by desktop-file-utils in Ubuntu)

was undone there
+debian/gnome-mimeapps.list usr/share/applications/

or that list isn't customized by Ubuntu and taking over our defaults