Hi Petr
Cc James
I fear we are hijacking Adithya's thread. Assuming the moderator splits this at https://moodle.org/mod/forum/discuss.php?d=470304#p1888056, I gave this future thread a new subject line.
First thing, I didn't know that the domain/path kind of Moodle instances allow "any editing teacher can easily gain admin access to all other site". I'm no security expert, but for me that statement also says, "any editing teacher can easily gain admin access to his Moodle site". Really? Or, do you mean the fact that Moodle empowers the teachers by allowing them to paste code (CSS and JavaScript) in to text fields? Well, I know that, and very happy with it, because in my environment (tertiary, govt. or semi-govt.) only teachers who are worthy of that title are being employed. Those who have gaps gets trained at work. The (remotely) possible black sheep will get a bang on their heads.
Now specifically to the domain/path URL, that is exactly how I created 30 Moodle instances under one sub-domain for the participants of a Moodle System Administration course. They could download (git) a number of Moodle versions, install them, work in them, back up them, upgrade them (within a range), delete them, recreate (by dropping the database), restore them. That was a highlight - apart from Mary visiting us on video link, judging from their feedback and seeing them visiting the course page months or even after an year after to refer to the notes.
Of course, I know (most of) the dangers of that setup. Therefore took a dedicated (mini) server, was careful to my abilities, and the configuration deactivated a couple of months later giving them to practice on their own. (I'm sue, I've discussed this setup at that time on these forums.)
Whatever, the point is, I will be unable to repeat that exercise with Moodle 5.1 and later if needed (unless I myself go through a Moodle 5.1 system administration course).