Can't install docker on my ubuntu, because of a "NO_PUBKEY 7EA0A9C3F273FCD8" error in apt-get update
You may want to double-check that the second step in Docker's documentation has been applied against your system:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
Without this, you will not be able to connect to the repo. I've just tested the installation steps on a fresh Ubuntu installation and everything has worked without any problem. Hopefully this is all you need to do 👍🏻