The apt-key command manages keys that are responsible for verifying the signature of application package repositories. Now, whenever you use the apt-key command, you will receive the message: Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)). It means that the apt-key program is now deprecated. Now we should use trusted.gpg.d to manage keyfiles. Translated into human...