Comment 10 for bug 1926223

@Jakuro: This just tricks udpkg in the install environment into thinking that it is already at 2.31-0ubuntu9.3 so it doesn't try to update, and therefore doesn't fail. It's is 9.* to catch 9 in the focal installer and 9.2 in the focal-updates installer.

A simpler sed is probably sufficient, and less prone to typos. This one is untested, though.

sed -i -e 's/Version: 2.31-0ubuntu9.*/Version: 2.31-0ubuntu9.3/' /var/lib/dpkg/status