An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://repo.mysql.com/apt/ubuntu focal InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 467B942D3A79BD29
Solution
sudo apt-key adv –keyserver keyserver.ubuntu.com –recv-keys 467B942D3A79BD29
If “467B942D3A79BD29” is different – just change it for value from error message.