There is some good info spreading across threads, but I figured it was time to consolidate what works (and what doesn't) with third party radios.
CaptainRob got this started with a great set of posts beginning here,
With that info, I bought these items:
Maestro's ADS-MMR RR - this box converts all the vehicle side info into something the radio understands. Mostly vehicle and radio agnostic. Lots of cables included in the box.
Maestro's iDatalink ADS-HRN-RR-CH3 harness. Vehicle specific. This plugs into the vehicle radio harness & OBD2 connector and connects to the Maestro ADS-MRR box
Kenwood DMX7704s - double din with support for Android Auto and two cameras. No navigation. Oddly, it does have a GPS antenna, but that is only used to set the time.
Metra 95-6523 - Dash kit for Promasters (2014+)
Metra 40-EU10 - antenna to radio adapter cable
USB A Male to USB Mini Female adapter - This converts the connector inside the dash to the connector on the back of the Kenwood. The USB port in the dash, under the steering wheel, connects to this. This allows for Android Auto (and probably car play too).
I used some nails to push into each of he 4 holes on the face of the radio to release it from the dash.
To configure the maestro, you need a Windows machine with IE. Login to the Maestro site, connect the MMR-RR to your PC (usb) and walk through the steps to identify exactly which factory radio and new radio you have. There is an option to reprogram the functions of the steering wheel buttons.
After you configure your MMR-RR, there are links on the web site for wiring diagrams and operating manuals. These are specific to your setup, so they are very easy to follow. You do need to splice the Maestro wiring harness to the radio harness. I used crimped insulated spade connectors because I know this radio will not last forever.
The dash kit needed a couple of screws to secure it to the dash, so I reused some from the factory brackets that I removed. Overall installation was straight forward. In order to run the microphone (OK Google!) and OBD2 cable up to the back of the radio, I had to remove the lower center stack and cup holder. The cup holder just pulled out. The center stack had 4 torx bolts - two under the cup holder.
I removed a UConnect 5.0 radio. With the new setup, all radio functions work. Steering wheel controls work. The backup camera has a dedicated button on the radio and engages when I shift to reverse. Back up sensors work and display. some vehicle gauges are available (OBD2 sourced) on a dedicated screen. Door open indicators show on the vehicle info screen. I think the back doors (I have two) only show as a single entity. The radio is updating the dash clock. There are a couple of vehicle specific config item accessible from the radio, for example Trip B data display on/off. The Maestro allows for prebooting the radio when the doors unlock and continued power (for a defined time) after vehicle shut down.
I have not connected any rear speakers. (I'm not even sure where those wires are in the body.)
Issues right now: TPS data shows, but 3 show 91 PSI. only one is showing the correct value (62). I have a bluetooth OBD2 device I need to hook up for diagnostics. On the vehicle info screen I have a flashing P in box. I presume that is supposed to show the parking brake state, but it doesn't.