Mobile Linux actually has a really nice car navigation app: https://open-store.io/app/pure-maps.jonnius

It uses OpenStreetMap data and can be (optionally) used fully offline.

The waydroid gapps image comes with Google services. I'm trying to install from Google play, but it says my device isn't compatible. I've read that I have to self certify it in order to get Google play protect certification working. Maybe that's the problem. I'll try and see what happens.

there's a magisk module for microG Androids (https://github.com/sn-00-x/aa4mg) that brings in some proprietary AA stubs that work in that environment. It pulls in the necessary gplay dependencies (assistant aka velvet, tts engine(?) and Maps). You could use https://github.com/casualsnek/waydroid_script and load this module in magisk.

Then there's a thread where users assemble a patchset for ROM / Android GSI builders to use AA as a user app, making it more accessible than it being a priv-app - https://github.com/microg/GmsCore/issues/897