Linux-Container Upgrade won't work

[Nadja]

Hello everyone,

I have an ASUS Chromebook. Accordingly, the operating system is ChromeOS. For a long time I have gotten notifications that an upgrade for my Linux Container is available. These upgrades have never worked. With the help of a friend who’s a programmer, we have found the issue in the Linux terminal and did the upgrade manually (the current version is Debian 9 and the newest is Debian 11). We used this for reference: https://www.digitentic.com/upgrading...-to-debian-11/
And it worked. Meaning: the Upgrade went through with no errors. Then the only thing left was to restart, which I did and: I still have Debian 9, not Debian 10 despite no issues.
Does anybody have any idea why this happened and how to fix it?

I would be very grateful for any tips.

Ps: for context: when I put sudo aptitude dist-upgrade in the Linux terminal now, this is what comes out:
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.

[Bruce]

not many Linux users on the forum I believe.
but from a troubleshooting point of view, I would get the latest build of Debian onto a bootable USB stick and do a fresh install rather than an upgrade.

of course, backing up your files first.

or instead of going from 9 to 11, try going to 10 first, than go to 11.