[Merge] ~juliank/livecd-rootfs:deb822-sources into livecd-rootfs:ubuntu/master

[Julian Andres Klode]

Pushed v2:

- Enabled backports by default (I did not see that!)
- Enabled restricted, multiverse security updates
- Replaced tweaked with adjusted
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https://code.launchpad.net/~juliank/livecd-rootfs/+git/livecd-rootfs/+merge/458366
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