GPG error: http://in.archive.ubuntu.com/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32 NO_PUBKEY 871920D1991BC93 code example

Example: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6494C6D6997C215E