I don't understand because it is comunicating with the debian servers correctly.
It just fails at Armbian's
This is a new install
root@rockpi:~# apt-get update
Hit:1 http://security.debian.org stretch/updates InRelease
Ign:2 http://cdn-fastly.deb.debian.org/debian stretch InRelease
Hit:3 http://cdn-fastly.deb.debian.org/debian stretch-updates InRelease
Hit:4 http://cdn-fastly.deb.debian.org/debian stretch-backports InRelease
Hit:5 http://cdn-fastly.deb.debian.org/debian stretch Release
Ign:7 https://apt.armbian.com stretch InRelease
Err:8 https://apt.armbian.com stretch Release
server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
Reading package lists... Done
E: The repository 'https://apt.armbian.com stretch Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.