[MTCD  Android Head Units Q&A] maxiauer:
Yes, and it worked, at least on the PX-5 (I just got a used PX-6 to upgrade my unit).

The good: The solution is wired instead of Wireless and starts automatically each time the unit starts (no need to enable screen mirroring or some WiFI hotspot on my phone to create a WiFi network)

The bad: ehhh... is not that "clean"and requires some effort

Here it is what I did:

I acquired a LCD screen + a controller with an HDMI input. Something like this (sorry, I do not have the specific link to the one that I actually bought)

https://www.aliexpress.com/w/wholesale-hdmi-to-50-pin-lcd-board.html?catId=0&initiative_id=SB_20230809181455&SearchText=hdmi+to+50+pin+lcd+board&spm=a2g0o.order_list.1000002.0

NOTE -> Make sure that the resolution of the external screen is EXACTLY the same resolution of your unit screen !!!

I put the control board under my dashboard, next to the stereo unit and I acquired an extension for the flat cable that goes from the control board to the unit. I was able to use the junction of 2 plastic pieces on my dashboard to make the flat cable go through it.

Then I acquired a USB -> HDMI adapter with DisplayLink protocol support. Here the critical point is to support DisplayLink protocol. Again, the link is only an example of a similar product

https://www.amazon.com/Direct-Access-Tech-5464-DisplayLink/dp/B07JKKRNX3

After that I installed DisplayLink app for Android in order to mirror the screen, and send that compressed data via USB to the USB-HDMI "adapter". Here:

Android Apps by DisplayLink on Google Play

DisplayLink technology makes it simple to connect any display to any computer that supports USB or Wi-Fi.

play.google.com

I do not recall if I used DisplayLink Presenter or DisplayLink Desktop.

The solution worked but had a big problem: Android sent the audio to the "HDMI port" emulated via DisplayLink. So I installed an app that allows to forcefully switch the audio output to a specific port. I contacted DisplayLink to see if there was another solution or if they would enable some set-up on their app, but they said it was not on the roadmap, and actually thanked me for the info and published my proposed solution in their Support page

Configuring DisplayLink audio on Android – DisplayLink Support

support.displaylink.com

Mirroring worked OK, audio returned back to the normal analog output, and I did not notice any significant drop in performance.

The dream would be to be able to tell Android that there're 2 screens and send Maps app video to the external one, and keep Music and Home screen on the Unit screen. But as far as I know at that point in time Android as an OS did not support 2 screens. This might have changed recently now that the Pixel Fold has 2 physical screens (but only one is active at a certain time)

NOTE: @Pavel-71 is right. The PX6 CPU-board has a mini-HMI port on itself, and it can be enabled on the FactorySettings. I got a PX6 a few weeks ago and I was going to test this but bad luck, on my unit motherboard (which is old and different from others I have seen) that port is just next to some metal capacitors that blocks it when you install the new CPU board. (see red circle in the picture). If you do not have that capacitor, I'd suggest you try to get a PX6 board with the mini HDMI. If it doesn't work, well, at least you will get a way faster CPU...

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