If you check on Github, you'll see that I released MoodleBox 4.11.0 a few weeks ago, with Moodle 5.1. It is not a beta, but a stable release, you can use it just like @Ralf Krause, who has certainly built its own image using the software I developed.
No image was released (yet), as I had a few problems building it, and no time to investigate the problems.
