What you’re asking for is fairly unrealistic. The only way this could work sustainably would be for something to exist where you host your own tile server and routing service and patch that into OSM. Otherwise, even if the app itself is open source, the backend will cost money to run and will be proprietary.
The reason that OSM is able to be fully open source is because you host the tiles on your phone and do the routing calculations locally.
I can’t think of any reason the backend can’t be open-source too.
It costs money to host something like that. You want low latency, real-time routing and tile-rendering? Even more money. Sure, it could be funded by donations or something like that, but I’m not holding my breath.
Could be self hosted
If you’re willing to spend all the money on setting up and running a server, why not just spend way less money to get more phone storage and use OSM?
No
The current FOSS offerings do the calculations on your device, so you’d need the maps downloaded locally. The small apps that stream their tiles from OSM/Jawg/ESRI/Mapbox etc. don’t support navigation because of this
Not FOSS but the closest thing you’ll get to this is GMaps WV on F-Droid, made by the DivestOS team. Even that does not support navigation though, it only provides directions (usable for me, your mileage may vary…)
I don’t know the size, but Organic Maps may be rather small
Then there are these two:
https://android.izzysoft.de/repo/apk/io.github.janbar.osmin
https://f-droid.org/packages/com.junjunguo.pocketmaps/
But I have no experience with them
I like organic maps cause it does shit locally, offline. It has to download the maps though which is certain to be larger than 50mb. What you are looking for is a cloud based maps solution like google maps and you aren’t going to find that in foss space
Not under 50MB but there is: https://organicmaps.app/
And
I find Organic Maps best for driving and OSMAnd+ best for walks.
Organic maps can’t even handle addresses. How is this useful for driving?
Yes it can. You need to download the necessary maps first before you can search for addresses though.
It does handle addresses.
Not in the US. I have the world map and the los Angeles maps. It is incapable of recognizing any address that I give it
Is the area properly mapped in OpenStreetMap? Organic Maps uses OpenStreetMap data, if addresses are not present there, then it’s up to the users to add them.
Looking for the same thing for Linux fwiw, with live turn by turn navigation and GPS support.