Tried it for while, works with GrapheneOS and Android Auto well enough.
What I absolutely can’t stand is the routing. It once tried to send me through residential Oakland on some Manhattan-grade staircase labyrinth instead of just taking normal streets.
Honestly I've seen google maps suggest some absurd routes, especially to avoid 1 minute of traffic on the motorway.
Always best to double check the routing suggestion.
One of the routing options in CoMaps is "avoid stairs". Not enabled by default. See ≡ → Settings → Routing Options.
(CoMaps is the open-source, non-profit community fork of Organic Maps.)