I'm also really hoping for that. Some kind of local OSM map server that all apps in the ecosystem call to provide geodata.
I run OSMand, StreetComplete, Organic Maps and Magic Earth on my phone. I need all of them to download the exact same geo data. And for convenience reasons, I usually load entire countries. It's so annoying having to download a country in app #3...
Also, mobile apps often have strict privacy lately around what files they can access: they're not just sitting on the filesystem, they're in access-controlled app-specific folders. That's good for privacy/security, but a dealbreaker for first-class sharing of information between apps.
Am I misinterpreting something? This is because of the underlying OSM data. So one should add these places to OSM so downstream apps will show the places you want, right?
Navigation apps such as OrganicMaps and OsmAnd filter OSM data, and package it in way that takes up less space. I.e., it will omit individual trees, manholes, etc. It also omits tags from OSM objects that it does keep.
This is all to to make it possible to fit enough maps on a phone and also there have code that can use that data (for searching and displaying)
Take for example Motorhome stopovers (I have edited at lot of those). OsmAnd has name, opening, hours, power_supply, fees, dump_stations, toilets, showers, phone numbers, website, and a few more tags. But not water_point (although it has drinking_water which is not used much for stopovers).
OrganicMap has much fewer tags for motorhome stopovers.
Ideally any app using OSM data would enable contributing to the underlaying map data. But that's probably not how it works.
For what it's worth: I like Organic Maps for being more lightweight, quicker rendering & simpler configuration than OSMand. But it (still? haven't used in a while) does lack some useful features like points of interest (supermarkets, gas stations & such).
Would be nice if it were easy to share (offline) map data between apps. Download in app A, backup on sd card , use from app B, C, D, or on other device by swap/copy sd card. Maybe it's possible, but I haven't figured out how (on Android). At least it's not easy/obvious/automatic.