pi@raspberrypi:~ $ sudo -i
root@raspberrypi:~# apt-get update
Hit:1 http://raspbian.raspberrypi.org/raspbian buster InRelease
Hit:2 http://archive.raspberrypi.org/debian buster InRelease
Ign:3 https://updates.victronenergy.com/feeds/venus/release/packages/raspbian-jessie jessie InRelease
Hit:4 https://updates.victronenergy.com/feeds/venus/release/packages/raspbian-jessie jessie Release
Ign:5 https://updates.victronenergy.com/feeds/venus/release/packages/raspbian-jessie jessie Release.gpg
Reading package lists... Done
E: The repository 'https://updates.victronenergy.com/feeds/venus/release/packages/raspbian-jessie jessie Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@raspberrypi:~#