Another note for future generations: The https://gist.githubusercontent.com/Abdess/3ed9ed1d42821d00a5cf2481870df26f/raw/tutor-mysql8utf8mb4.yml plugin has
image: docker.io/mysql:latest as the mysql to be used. That worked for me through MySQL 8.3.0. However the latest MySQL has started deprecating CLI passwords. (as encountered here
So the mysql -uroot -pXXXXXXXX command mentioned above will break if you use image: docker.io/mysql:latest as is default in that plugin.
I currently recommend using image: docker.io/mysql:8.3.0 instead, if you want to use the above instructions.