With MySQL 8.0.11 I'm unable to log in with users that had been working fine under previous versions (at least 8.0.0, perhaps even more recent than that).

mysqli_real_connect(): The server requested authentication method unknown to the client [caching_sha2_password]

mysqli_real_connect(): (HY000/2054): The server requested authentication method unknown to the client

See also https://dev.mysql.com/doc/refman/8.0/en/authentication-plugins.html

I'm using QA_4_8.