Official Document Entry:
https://dev.mysql.com/doc/
Generally choose MySQL Server version entry:
https://dev.mysql.com/doc/refman/en/
On the right side there is a version selection:
such as the entrance to the installation tutorial:
Https://dev.mysql.com/doc/refman/5.7/en/installing.html
There are also a number of official tutorials:
The official English version is available, using chrome translation.
This tutorial does not have the installation method of apt source, the entrance is here:
https://dev.mysql.com/doc/mysql-apt-repo-quick-guide/en/
Summarize:
In fact, the online circulation of the tutorials are not too authentic, if you want more accurate and more comprehensive tutorial please refer to the official documentation.
https://www.mysql.com/
MySQL official tutorials and installation tutorials and configuration details portal for each platform