I found that the docker stable repository is not signed, and I can't believe that. Can anyone confirm please?
Following https://docs.docker.com/install/linux/docker-ce/ubuntu/#set-up-the-repository, the "set up the stable repository" section:
% add-apt-repository \
> "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
> $(lsb_release -cs) \
> stable"
. . .
W: GPG error: https://download.docker.com/linux/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7EA0A9C3F273FCD8
E: The repository 'https://download.docker.com/linux/ubuntu bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
$ apt-cache policy docker-ce
docker-ce:
Installed: (none)
Candidate: (none)
Version table:
