I tried that manually and the result looks good. I also tested the
installation of "openjdk-11-jre-headless", did not work before as
reported by Roberto, works after.

It is really about doing what that dpkg.conf does, not about making
sure that package can be installed .. but it can now.

The ubuntu scripts make sure all is like dpkg.conf by re-installing all
packages that deployed anything to the excluded paths in their
containers and livecds. But that is really not nice so i would not want
to copy that pattern.

https://git.launchpad.net/livecd-rootfs/tree/live-build/auto/build#n197