Debian 11 "bullseye" released

If sources.list is *unmodified from the installation* (using an official installer image), it should use release codenames (i.e., buster for Debian 10) for stable releases and late testing images instead of stable/testing. In that case, you wouldn't get that message. On the machines I manage that I've yet to migrate to Debian 11 I didn't get any notification, but I did get a similar notification stating that bullseye had become the stable release. Personally, I prefer to keep the distro codenames in sources.list instead of using stable to ensure the distro version upgrade is on my terms (regarding timing), but to each their own :)

PD: Note that the security repo has migrated on debian 11 from stable/updates to stable-security ; luckily for me, on all the machines I've upgraded so far that was the biggest hurdle.