I had this old Virtual machine running Jessie. Turnkey Linux/Debian
root@TurnkeyLamp apt/sources.list.d$ uname -a Linux TurnkeyLamp 3.16.0-6-amd64 #1 SMP Debian 3.16.56-1+deb8u1 (2018-05-08) x86_64 GNU/Linux
In order to update
add check-valid-until=no to the archive Debian repository
deb http://archive.turnkeylinux.org/debian jessie main deb [check-valid-until=no] http://archive.debian.org/debian jessie-backports main deb http://httpredir.debian.org/debian jessie main deb http://httpredir.debian.org/debian jessie contrib # deb http://httpredir.debian.org/debian jessie non-free