Step 1 - Install the Armbian PGP key and update your APT sources   Install armbian.gpg to /usr/share/keyrings/armbian.gpg  (mode 644) You can use a copy from another one of your SBCs, or... ... you can download and install like below (thanks @BrewNinja for the example) touch /usr/share/keyrings/armbian.gpg chmod 644 /usr/share/keyrings/armbian.gpg wget https://apt.armbian.com/armbian.key -O - | gpg --dearmor >/usr/share/keyrings/armbian.gpg