Comment 1 for bug 1925395

Hi Paul and thanks for this bug report. I agree that's currently a cloud-init limitation.

I have a different and possibly better (but untested!) workaround to suggest: use write_files to dump the gpg key to trust to /etc/apt/trusted.gpg.d/. This should prevent the "duplicate entry" warning, and adding keys to trust in this way is better than using apt-key (what "sources" does, see the deprecation warning in apt-key(8)), but I agree it should be better integrated in the repositories config.

[1] https://cloudinit.readthedocs.io/en/latest/topics/modules.html#write-files