Is there a way to overlay property lot lines (aka land ownership maps) on the map of preferably a mobile FOSS application? I like OSM And and I know there are ways to make certain obscure things work. OnX Hunt has this feature but I don't want to use the application
@sic_semper_tyrannis
If you can get the parcels from the municipality then you can probably give them a false OSM tag that renders and convert to show on OsmAnd via OsmAndMapCreator (then sideload them). It might be best to convert the addresses to OSM format too so they display.
Alternately there are two apps for putting QGIS projects on a mobile phone: QField and Merging/Input. They are meant for data collection but can be used to just display things as well.
Should indeed be doable, but please: do not upload this data into the "real" OpenStreetMap.org. We don't do parcel data (it is not verifiable on the ground), and imports are something that should be done with care.
However, you can use the tools. Use JOSM to prepare the data and convert it to a .osm-format on your local computer. Then use the OBF-creator to make an OBF file which you can drop at the right location on your phone. The map creator is right here :https://osmand.net/docs/versions/map-creator