It looks like the only patch that is intentionally different between Debian and Ubuntu is that 0002-desktop_file.patch is not applied on Ubuntu.
I think that patch could be either removed or applied on Ubuntu too. If you decide you do want to continue to have different behavior on Ubuntu, you could use something like https://salsa.debian.org/desktop-themes-team/numix-gtk-theme/commit/488a7f83 instead. Thanks, Jeremy Bicha
