Microsoft Store offered Ubuntu 20.04 LTS, so that's what got installed (on WSL1). Following Setup works until there's an error with mysql-server. Doing sudo apt install mysql-server produces in /var/log/mysql/error.log:
[ERROR] [MY-012585] [InnoDB] Linux Native AIO interface is not supported on this platform. Please check your OS documentation and install appropriate binary of InnoDB.