On 18.08.21 at 06:51 Richard Forst wrote:
$ sudo cat /etc/apt/sources.list # security deb http://security.debian.org testing-security main contrib non-free deb-src http://security.debian.org testing-security main contrib non-free
See the new pattern:deb http://security.debian.org/debian-security bullseye-security main contrib non-free deb-src http://security.debian.org/debian-security bullseye-security main contrib non-free
You are missing the debian-security part after the /