You say doesn't pay for devices, but what about treatments with braces, does insurance pay for it?

In adults they only pay basic braces if they come along with surgery. 

In kids they spend a lot of money for orthodontics. Unfortunately a lot of kids are treated with extraction and retraction and therefore suffer from TMJ later on. 

Now theres a debate whether they should reduce the money for orthodontics. I hope the discussion about the cause of crooked teeth will come to Germany, too. 

Even in the U.S., whether or not medical insurance covers orthodontic treatments relies upon the ability of the provider, and to some extent the patient and their PCP/specialists (ENT, sleep doc, pain management), to argue medical necessity. I.E., patient has sleep apnea/UARS, research shows palatal expansion improves and/or resolves some apnea/UARS (stanford 2017 DOME study), non-surgical expansion is evidenced as being comparable in it's affects on the nasal passages and palate (research by Singh on DNA/Vivos as well as others) therefore, non-surgical expansion is medically justified and conducive to the patients care.

It may require you get your ENT or sleep doc or the orthodontists to get on the phone with each other, and then conference call a medical director. Or just one of them call the medical direct. Just make sure whoever communicates with the insurances understands the physiology of respiration and breathing, has a good handle on the orthopedic consequences of craniofacial issues, and is invested in getting you the right help, not just some help. For example, I'd feel personally disserviced if a provider went on the phone trying to get a non-surgical treatment plan approved, and got off the phone with approval for surgery, which is unlikely, but possible, given that 'everyone knows surgery works' and if you come at a medical director with information they're unfamiliar with they may try to compromise by offering what they are more familiar with.

So, getting insurances to cover this is possible, it's just currently quite difficult based upon your region. If you demonstrate you're willing to work hard in helping make it possible, you're more likely to get this done. For example, instead of pushing all tasks onto the provider, take the effort to gather all your medical records. I sorted through over 600 pages of documentation, found the one's with pieces relevant to problems I understand to be related to my facial growth (airway, sleep, myofascial pain in head/neck/back, psych issues, GI issues, more...a lot goes wrong when jaw growth impairs the airway) and then highlighted the parts of those pages most relevant. So, 600 pages became 60 and those 60 could be skimmed in a few minutes by reading the highlighted portions and a good understanding of my problems and the necessity of treating them could be understood. That's the type of work I think is necessary and if it works I'll be sure to let others know. That much effort though is well outside what a doctor has time for. Our medical system is broken, and to make it work sometimes requires patients to become very involved in their care.