I am currently running Debian 8.1 Jessie and am considering updating to Debian 9 Stretch so I can install the newer version of TeamTalk from www.bearware.dk/.
I am using this article and changed every instance of J/jessie to S/stretch, but I am getting these errors.
W: Failed to fetch http://mirrors.linode.com/stretch/dists/stretch/main/source/Sources 404 Not Found [IP: 2600:3c01:1::607e:6379 80] E: Some index files failed to download. They have been ignored, or old ones used
I was able to get to
Get:16 http://security.debian.org stretch/updates/non-free Translation-en [691 B] Fetched 35.9 kB in 4s (7,377 B/s)
So, it was able to download most of them from the debian.org or security.debian.org site.