[Merge] ~toabctl/livecd-rootfs:new-ubuntu-oci into livecd-rootfs:ubuntu/master

[Thomas Bechtold]

@Dimitri, I'm happy to work on the suggestions but currently I don't want to change what is currently in our docker images available on dockerhub. After having the whole pipeline from building to publishing changed to use this new project, I can work on your suggestions.

I plan to SRU this to way back to bionic.
Can you merge & release this so I can start looking at the SRU process (I never did that so that's new to me).
Thanks for the review!
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https://code.launchpad.net/~toabctl/livecd-rootfs/+git/livecd-rootfs-1/+merge/401596
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