I just migrated my MoodleBox up to 3.12.0.
I saved the database and the folders moodle and moodledata from my old MoodleBox ... 50 users, 8 courses, 58 additional plugins, and a lot of content for my teachers workshops. I copied the new MoodleBox image to a new microSD card and put it into my Raspberry Pi 4B. The MoodleBox 3.12.0 started up as an empty Moodle as Nicolas configured it. But I wanted to get all my settings, all my users, all courses, all plugins, and all my content.
I deleted all tables in the database and imported the database backup moodle.sql.gz using the Adminer tool. I deleted the folders moodle and moodledata. I restored the folders moodle and moodledata from my backup. I rebooted the MoodleBox and my old MoodleBox was migrated to the new MoodleBox 3.12.0.
Yes, I added the 5th anniversary image manually into a new text block because this block and its content was lost when I deleted the database and the moodledata for the migration of the old MoodleBox. Yes, I also must edited the first summary block to set the new version and date.