Well, it is working for me (i.e. hosting OpenSprinkler using https with apache an a Raspberry Pi). The only thing, that I do not do is hosting the UI Assets on another server. I guess you are doing this for a certain reason like that you do not have internet access in your garden maybe? Sounds like this causes the error maybe… When you get the TypeError – do you also maybe have a 404 Not Found error in the Browser’s DevTools network tab?
I would try without hosting the assets on another server and see if that works. This way you can at least narrow down the bug/problem.