You maybe read my post about my first smarthome gadget, the Nanoleaf Aurora.
The setup was a bit pain in the ass, but I managed to do it though the app is crap at the moment. With Apple Homekit it worked like a charm - until I updated to iOS 11 - again. Since WWDC I installed iOS 11 on my iPad Pro and iPhone 6s, it worked „ok-ish“ but not perfect. Even wth beta 2 released some days ago I still miss the smoothness of iOS 10.3. Anyway, today I wall-mounted the Aurora and for this I had to disconnect it from the mains and of course wifi.
The setup afterwards was impossible so my guess was it’s iOS 11.And it was. While I downgraded my iPhone and iPad Pro I tried the iPad Air 2 of my girlfriend (still running iOS 10.3) and it worked instantly. Looking forward to have my devices back to iOS 10 I was confronted by a failure during downgrading the iPhone. It got stuck in recovery mode and I didn’t get it back to life.
I don’t know what went wrong but what I know is that I will have to visit my local Apple store and probably pay a huge amount of money to get it back working. So screw you, Apple by providing a software like iTunes which is the worst in the whole Apple universe. Of course I tried other solutions I found on Youtube and Blogs but all turned out to be non-free tools which won’t do anything until you buy them - not knowing if they will work out for you. I hate this non-transparency.
Anyway, I guess I will spend some hours in the store tomorrow and I've got no phone for the next couple of hours. I have to use my iPad - which survived the downgrade perfectly - as my alarm clock and communication central.
Wish me luck!
UPDATE
It's back! 
This morning I made an appointment in my local Apple store for the Genius Bar later in the afternoon. It turned out that there is a bug in iOS 11 beta 2 which causes phones to end up in the "restore loop" like my device did. Currently you are not able to go back from iOS 11 beta 2 to iOS 10.3.2 which iTunes tries to bring on during the attempts of restoring. If you don't have access to an IPSW package of iOS 10.3.3 beta 4 then you might have to go to the store, too. If you do, just flash the device like you always did in the past - by holding down the option key while pressing the "restore" button in iTunes. This allows you to select an IPSW image file.
This was my first service case with Apple and I have to say that it went fluently and all involved people were very friendly and professional. Good work, people from Dresden's store!