The repository 'http://http.us.debian.org/debian stretch Release' does not have a Release file

I am trying to setup Debian repositories on a router that runs a Debian-based EdgeOS. I am following this instruction here . After I add the repository, I get the following error. user@ubnt# sudo apt update Ign:1 http://http.us.debian.org/debian stretch InRelease Err:2 http://http.us.debian.org/debian stretch Release 404 Not Found [IP: 64.50.233.100 80] Reading package lists... Done E: The repository 'http://http.us.debian.org/debian stretch Release' does not have a Release file. 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. [edit] When I look inside the apt directory I see the following: user@ubnt# ls -lha /etc/apt/sources.list.d total 4 drwxr-xr-x 1 root root 232 Jun 24 19:38 . drwxr-xr-x 1 root root 232 Oct 20 2022 .. -rw-r--r-- 1 root root 80 Jun 24 19:40 stretch.list [edit] user@ubnt# cat /etc/apt/sources.list.d/stretch.list deb http://http.us.debian.org/debian/ stretch main contrib non-free # stretch # [edit]