//download 'link'.docker.com/linux/ubuntu Bionic Inrelease' Is Not Signed - The Repository 'https

Using a repository for a different Ubuntu version (e.g., Bionic on a Focal system).

If you are on an older system that still relies on the deprecated apt-key method, you might need to manually refresh the key. List your current keys to find Docker: sudo apt-key list Using a repository for a different Ubuntu version (e

The most frequent cause is a missing or outdated GPG key. Modern versions of Docker require adding the key to a specific keyring directory rather than the old apt-key method. Using a repository for a different Ubuntu version (e