Bullseye config/update errors

Are Trinity mirrors not yet adapted to the existence of Bullseye? I'm having no luck finding the instructions page for setting up Debian Testing. :-( All I tried was "sed -i 's/buster/bullseye/g' sources.list" with an old sources list file for Buster. After that generrated 404, I tried switching from bullseye to testing, which gets farther, but not without errors. # apt update Hit:1 http://ftp.debian.org/debian bullseye InRelease Ign:2 http://mirror.xcer.cz/trinity-sb bullseye InRelease Err:3 http://mirror.xcer.cz/trinity-sb bullseye Release 404 Not Found [IP: 91.241.23.210 80] Reading package lists... Done E: The repository 'http://mirror.xcer.cz/trinity-sb bullseye 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. # apt update Get:1 http://ftp.debian.org/debian testing InRelease [117 kB] Ign:2 http://mirror.xcer.cz/trinity-sb testing InRelease Err:3 http://mirror.xcer.cz/trinity-sb testing Release 404 Not Found [IP: 91.241.23.210 80] Get:4 http://ftp.debian.org/debian testing/main amd64 Packages [7,916 kB] Get:5 http://ftp.debian.org/debian testing/main Translation-en [5,981 kB] Get:6 http://ftp.debian.org/debian testing/main amd64 Contents (deb) [36.4 MB] Get:7 http://ftp.debian.org/debian testing/non-free amd64 Packages [90.2 kB] Get:8 http://ftp.debian.org/debian testing/non-free Translation-en [90.3 kB] Get:9 http://ftp.debian.org/debian testing/non-free amd64 Contents (deb) [858 kB] Get:10 http://ftp.debian.org/debian testing/contrib amd64 Packages [52.4 kB] Get:11 http://ftp.debian.org/debian testing/contrib Translation-en [45.6 kB] Get:12 http://ftp.debian.org/debian testing/contrib amd64 Contents (deb) [102 kB] Reading package lists... Done E: The repository 'http://mirror.xcer.cz/trinity-sb testing 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. # cat /etc/apt/sources.list # deb http://mirrors.kernel.org/debian/ testing main deb http://ftp.debian.org/debian/ testing main non-free contrib #deb-src http://mirrors.kernel.org/debian/ testing main #deb http://security.debian.org/ testing/updates main non-free contrib #deb-src http://security.debian.org/ testing/updates main deb http://mirror.xcer.cz/trinity-sb testing deps-r14 main-r14 deb-src http://mirror.xcer.cz/trinity-sb testing deps-r14 main-r14 -- Evolution as taught in public schools is religion, not science. Team OS/2 ** Reg. Linux User #211409 ** a11y rocks! Felix Miata *** http://fm.no-ip.com/