Can't install Mysql on Linux -- Mysql website failing?

The answer you linked to is wrong, though it might have accidentally worked at the time it was posted.

MySQL does not provide RPMs for Amazon Linux (either 1 or 2). The instructions given in that answer are for CentOS 7, and only work on RHEL 7, CentOS 7, or actual identical clones (Oracle, Scientific, etc.). Amazon Linux and Amazon Linux 2 are not guaranteed to be compatible with CentOS packages, or indeed, with packages from any other distribution.

If you need to use such packages, you also need to switch your Linux distribution.

Michael Hampton is correct, please refer supported platforms https://www.mysql.com/support/supportedplatforms/database.html, If you still want to give try check http://repo.mysql.com/yum/mysql-connectors-community/fc/ this is indexed mysql repo and find the appropriate connector url for you repo.