I agree there are good applications available, but OSMAnd is an Android app, you'd need some sort of compatibility layer for it to run on stock Linux. I think there is work going on for that happen, but it's not there yet. The project I can recall is Shashlik, there are one or two others as well.

I think Android app compatibility is necessary for a Linux phone. You won't be able to use Play Services, but a lot of apps do not require that. Android compatibility would for instance give you WhatsApp. It also gives you access to hardware like activity monitors (Garmin and Withings apps don't require play services), which otherwise is very unlikely to be supported. And also sophisticated public transport apps like Moovit.