I recently switch https://onthegomap.com from google to OSM for walking paths between points. The trail quality is much better where I live (Massachusetts) but I have been getting a lot of complaints from people all over the world that it no longer has their trails. I wonder what the lowest friction way to get my users to help contribute trails to OSM would be?
A built-in editor that's specifically targeted to what interests them.
There's an app called OpenVegeMap which shows you vegetarian and vegan restaurants nearby. It also allows you to add and edit this information. Found a nice vegan bistro? You're just two clicks away from adding a missing tag about it to OSM. Just this and nothing else.
As Max Erickson says, they need their own OSM account. You can write your own editor, which submits changes to the OSM API. Users can authorise your editor to edit in their name via OAuth. Once someone has auth'ed your app, they can stay entirely within your app.
But be careful that you don't lead your editors to think this isn't a global database that others use, or other OSMers will be annoyed.,
They're both significantly worse than maps focused on hikers.