There are a lot of mapping resources online and some can be fairly complex to use. Developing a route for a mixed terrain ride can be challenging. Recently, Strava moved a lot of their mapping tools behind a pay wall. I have found that Gaia GPS is a good replacement, although, most notably, it does not have a heatmap overlay.
Finding interesting roads and trails can be challenging. Gravelmap depends on users to upload activities. In contrast, Seeking Dirt uses goverment GIS data on road surface information, but unfortunately, currently does not include Maine. It is a fairly simple process to download road condition data from the Maine DOT. Navigate to MaineDOT Public Roads and select the Data tab. Then scroll to the Surface Type column, press the filter button and select the desired surface types. Then click the Download button and click the link under Filtered Dataset. Load it in JOSM or QGIS and overlay it on top of OSM tiles using a plugin to get the same results. Apparently, KML is a standard defined by Google Earth, so it may be possible to load it into the desktop Google Earth Pro application.
OpenStreetMap includes a surface tag, which can be queried and then displayed using overpass turbo.
[bbox:{{bbox}}];
(
nwr["surface"="unpaved"];
nwr["surface"="gravel"];
nwr["surface"="ground"];
nwr["surface"="dirt"];
nwr["railway"="abandoned"];
nwr["snowmobile"="yes"];
);
out body;
>;
out skel qt;Mapping sites designed for mountain biking like Trailforks can also be helpful in defining routes.
There are countless trails that are not formally maintained and access isn’t clear. Cities maintain GIS data including parcel boundaries and high quality satellite images that help with defining maps.