MySQL has been replaced by MariaDB since Debian 9 Stretch in 2017. MariaDB is a MySQL fork created by the authors of MySQL (e.g. Michael "Monty" Widenius) after Oracle bought Sun in 2009 out of distrust that Oracle is likely not a good open source project steward.
To install MariaDB, use the packages mariadb-server and mariadb-client.
To find official Debian documentation about specific programs, look for *.README and NEWS files inside the package itself, such as:
https://sources.debian.org/src/mariadb/1%3A11.8.3-1/debian/mariadb-server.NEWS
https://sources.debian.org/src/mariadb/1%3A11.8.3-1/debian/mariadb-server.README.Debian