sudo apt install apt-transport-https dirmngr
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb https://download.mono-project.com/repo/ubuntu focal main" | sudo tee /etc/apt/sources.list.d/mono-official-vs.list
--> tried with "vs-bionic", but same outcome/error
sudo apt update
--> I get this error:-
"W: GPG error: https://download.mono-project.com/repo/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A6A19B38D3D831EF
E: The repository 'https://download.mono-project.com/repo/ubuntu focal InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details."
I don't know what to do now, could you please advise how to fix.
sudo apt install apt-transport-https dirmngr sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF echo "deb https://download.mono-project.com/repo/ubuntu focal main" | sudo tee /etc/apt/sources.list.d/mono-official-vs.list --> tried with "vs-bionic", but same outcome/error sudo apt update --> I get this error:-
"W: GPG error: https://download.mono-project.com/repo/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A6A19B38D3D831EF E: The repository 'https://download.mono-project.com/repo/ubuntu focal InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details."
I don't know what to do now, could you please advise how to fix.