Android Auto - Currently I have Wireless Apple CarPlay when I get the car, this runs maps and music for me. This is a bit of a deal breaker feature for me. I have read in some places that this is simply not going to work on Graphene. Is this truly the case? No chance? No how? If so, perhaps Graphene is not the solution for me and I should look at an Alternative De-Googled OS - Any recommendations?
Android Auto relies on inherently privileged functionality that cannot be provided by GrapheneOS without allowing Auto/Google Play Services swaths of invasive privileged access throughout the system. The point of the Sandboxed Google Play is that it is granted only the same permissions that every other 'untrusted' app is granted, with most of its desired functionality being more than possible through non-privileged means, so long as the compatibility layer shows it how to function under such conditions. Some functionality is inherently privileged, however, and cannot function under the standard app sandbox.
It should be noted that attempting to have this functionality whilst also retaining a secure de-googled Android distribution may prove difficult as such functionality is either provided by a distribution including Google Play in its fully privileged form (which wouldn't be de-googled and suffers from a large service having highly privileged access, which is a large attack surface) or including something like microG, which uses methods such as signature spoofing to pretend to be Google services, which is a problematic prospect: Compromises to this service would allow the faking of app signature checks.
File Management - This appears to be a bit of a dark art. I have a MacBook Pro and have used a couple of different apps for file management, each app crashes regularly and fails to copy etc.. So, is there a reliable app to use for file management from Graphene > macOS?
There are a number of various apps for this functionality. Which apps have you used so far? The couple I can name off of my head would be the default Android File Transfer tool, and OpenMTP.