No me funciona, sigue apareciendome el mismo error.
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sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 69755F70D8D6D0C4
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --recv-keys --keyserver keyserver.ubuntu.com 69755F70D8D6D0C4
gpg: solicitando clave D8D6D0C4 de hkp servidor keyserver.ubuntu.com
gpgkeys: HTTP fetch error 7: couldn't connect to host
gpg: no se han encontrados datos OpenPGP válidos
gpg: Cantidad total procesada: 0