The initial version of this feature is now available in ODK Collect v2022.2.0. We now have documentation for the select from map question type and for attaching a GeoJSON file to a form. 
There are various examples in this post.
Some folks I've talked to have mentioned that the biggest piece missing is status information on device (e.g. I've already visited these places). We hear you! There's no perfect way to do this yet.
This form (+ geojson file) shows two techniques that get pretty close. @Megan_Schroeder @Matt_Berg @Ukang_a_Dickson @Ivangayton
The first involves pulling out the geometry so that the submission will be visible on the form map. The form map only looks for geopoint questions that are user-visible so I couldn't just use a calculate. Instead I put the selection and the pulling of the location in a field-list. If you want to pull out the geometry for other purposes you may be able to just use a calculate.
The second technique that form shows is filtering out locations that have already been visited on the device using last saved. It has limitations. The state isn't preserved across updates of the form definition. There's no way to "un-visit" a place. But it's pretty close and might work well for some scenarios. This is the same technique discussed in this thread but across submissions rather than repeats.
Please try these new features out and let us know how you're using them and what issues you're running into.
Our tentative next step in this general feature area will be to add support for traces and shapes.