You can still use Jessie and backports you just have to change a couple of things.
I take no credit for this I found the fix online and am using it on my Jessie box.
Change your sources to:
deb http://deb.debian.org/debian jessie main
deb http://deb.debian.org/debian stable-updates main
deb http://archive.debian.org/debian/ jessie-backports main
You can add contrib and non-free if you want
Then run:
echo "Acquire::Check-Valid-Until false;" | sudo tee -a /etc/apt/apt.conf.d/10-nocheckvalid
Jessie sources will still work.
Now you are running Devuan which should not have been affected by the change to the best of my knowlege.
According to:
You need to add the following
deb http://deb.devuan.org/merged jessie-backports main
deb-src http://deb.devuan.org/merged jessie-backports main
In both cases you can install from backports with:
apt-get install -t jessie-backports [name-of-package]
