Looks like there is now a "aluminum made" brackets.As I mentioned way back when, I purchased some 3D-printed brackets from a German enthusiast. While they did resolve a few of the issues mentioned above, they have not withstood the test of time very well. The mounting screw holes are stripped, even with careful tightening. The plastic has warped badly with summer heat and each one is cracked. Better than the metal brackets, but still unacceptable in my opinion. The guy who produces these is no longer willing to ship to the US, but they are available from the iBus app store. I would not recommend them, but if you already have an Xtrons I suppose this is the best option currently available.
Regardless though (coming from someone that has tried both), the Avin is still a better choice over Xtrons head unit?
Not having in-dash CD slot, approaching year 2020, is that even a factor? This is where i'm stuck on.What makes the Avant 4 unique is: t's designed to use the OE BMW aluminum navigation mount, which all US-Spec M5 have. I have this installed now and I'm very pleased with the fit. It's very secure and the reinstallation of the OE bracket has also restored support to both the upper and lower dash pieces. The lack of an optical drive also means this fits the E39 much better. No interference issues with the HVAC box and plenty of room for all the adapters, etc.
Wireless Carplay works like a champ, I'm very impressed so far. The Resler interface connection is integrated into the AVIN adapter harness, so no splicing or soldering required.
If you're in the market for an Android device, the Avant 4 is absolutely the way to go, particularly if you're starting with a Nav-equipped E39. At this point, I see no reason to bother with an Xtrons, Eonon, etc. Just order the AVIN and be done with it.