UserAgent: Mozilla/5.0 (X11; CrOS x86_64 10895.78.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.120 Safari/537.36
Platform: 10895.78.0 (Official Build) stable-channel soraka-unibuild (soraka)

Steps to reproduce the problem:
1. Install Linux (Beta)
2. Open Termina and run any apt-get command, eg update or install
3. 

What is the expected behavior?
Apt-get install or update should, and used to work fine

What went wrong?
Now I get errors related to 404 not avail at the repo:
@penguin:~$ sudo apt-get update 
Hit:1 http://security.debian.org/debian-security stretch/updates InRelease
Ign:2 http://deb.debian.org/debian stretch InRelease
Err:3 http://deb.debian.org/debian stretch Release 
  404  Not Found [IP: 151.101.8.204 80]
Ign:4 https://storage.googleapis.com/cros-packages stretch InRelease
Hit:5 https://storage.googleapis.com/cros-packages stretch Release
Reading package lists... Done
E: The repository 'http://deb.debian.org/debian 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.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Have tried uninstalling and reinstalling Linux (Beta) to no avail

Did this work before? N/A 

Chrome version: 69.0.3497.120  Channel: stable
OS Version: 10895.78.0
Flash Version: 31.0.0.108 

When I try simply browsing to one of the URLs that is erroring, it actually does come back as 404, so the source files aren't available. I noted that it changes the URL to a CDN source: http://cdn-fastly.deb.debian.org/debian