First thought

[DG97EEB]

I'm yet to find the exact alphabet, but there was a significant seam of Southern Germans writing in made up alphabets at the time.

Are there any examples other than runic alphabets?

I'm not sure you need to go as far as to have a mental illness to validate the script...

This is an oversimplification. It’s one thing to “write in a non‑standard alphabet,” and quite another to “write a non‑standard book.” In the case of VMS, it’s not just about the alphabet.

Here's one.. mid 15th I think...   

Read the Geheimschrift project documents.. I posted the link on JOjO's Bavarian thread..  I think that's a failure of imagination, honestly..  I'm personally getting to a point after almost a year day in, day out where nothing about this book is actually unusual... It's so very obviously of its time and place (by which I infer Germany/northern Italy) that the only thing we lack is the person that wrote it and what if anything it says... But we may never ever know, because so few manuscripts still exist...  I love the mystery, but I no longer look at it and find it strange..