I’ve looked at the Nabataean comparison and it looks sort of similar but not exact which led me to try to find a closer match. Nabataean is an ancient western Aramaic dialect. I looked around and believe I found a language closer to the demonic language than Nabataean, the closer match I found is called Sabean. Like Nabataen, Sabean is an ancient Arabian language, south Arabian. The ancient Sabean language made it’s way to Africa specifically Ethiopia. Modern Ethiopian, Ge’ez, resembles Sabean to this day, there was a time when there was a cross-over language, half-Ethiopian Ge’ez and half Sabean which is what I would say looks closest to the unknown demonic language. Again Nabataean could easily have been directly related to Sabean as they both are ancient Arabian languages.
Take a look at the Sabean alphabet and the Ge’ez alphabet and the demonic alphabet and judge for yourself.
I’ll occasionally look for more but I think it may be impossible to find a complete exact match as it is a lost language, possibly short lived cross over language, at least there is a match to the hour-glass shaped letter which I didn’t know had ancient Arabian ties until now.
Nabataean on the left, Demonic on the right
Cross over between Sabaean and Ge’ez (Ethiopian)
The extensive Ge’ez alphabet