Does Android Auto in Graphene still require Google Maps to be installed, or is there a shim? If not, I wouldn’t be surprised if Calyx writes one, once they implement whatever black magic Graphene devs came up with to make AA work.
As a related example, Calyx has a Google Photos shim, so you can use other galleries with gcam. I just added Calyx’s f-droid repository, and use that with my Graphene install.
For now, I’m happy using my Mazda CX-5’s built in navigation with bluetooth audio. It’s nice enough to tile both side by side, and it’s less fiddly than AA. But my next car might not be as favorable, so I’m glad to have AA as an option.