Love the idea of making one! I would join. But as far as already established communities, the http://www.diymobileaudio.com/ forum is by far the best place. Really knowledgeable people and they are really nice. They’ve helped with a few of my projects.
To answer your question, I would like to ask if you are specifically looking for a head unit running android, or just a head unit with a screen and can use android auto with your phone. If it is the latter then I would recommend kenwood or an alpine unit. If you have any questions about the specific model lmk. We can talk further based on your needs 👍
I noticed you noticing