Ao realizar update do SO o gerenciador de pacotes informa:
Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
Procurar a key com problema
sudo apt-key list
Localizar a chave com problemas no formato:
XXXX XXXX XXXX XXXXXXXX XXXXXXXX XXXX 86E5 0310
sudo apt-key export 86E50310 | sudo gpg --dearmour -o /etc/apt/trusted.gpg.d/nomedopacote.gpg
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5
sudo apt-key adv --refresh-keys --keyserver keyserver.ubuntu.com