This was a great question and solution!

I used it to pull the coordinates for 2 arcade expressions representing the start and end points of the line. I didn't try it in fieldmaps but I think it would work to have it calculate column values for the line start/end points but I don't think you can have it create a point that represents the start/end point.

//Find the start coordinates

var xval = Geometry($feature).paths[0][0].x

var yval = Geometry($feature).paths[0][0].y

function metersToLatLon(xval, yval) {

var originShift = 2.0 * PI * 6378137.0 / 2.0;

var lon = (xval / originShift) * 180.0;

var lat = (yval / originShift) * 180.0;

lat = 180.0 / PI * (2.0 * Atan(Exp(lat * PI / 180.0)) - PI / 2.0);

return [lat, lon];

}

var latlon = "";

var result = "";

var latlon = metersToLatLon(xval, yval);

result = Round(latlon[0], 6) + ', ' + Round(latlon[1], 6);

return result;

//Find the end coordinates

var xval = Geometry($feature).paths[-1][-1].x

var yval = Geometry($feature).paths[-1][-1].y

function metersToLatLon(xval, yval) {

var originShift = 2.0 * PI * 6378137.0 / 2.0;

var lon = (xval / originShift) * 180.0;

var lat = (yval / originShift) * 180.0;

lat = 180.0 / PI * (2.0 * Atan(Exp(lat * PI / 180.0)) - PI / 2.0);

return [lat, lon];

}

var latlon = "";

var result = "";

var latlon = metersToLatLon(xval, yval);

result = Round(latlon[0], 6) + ', ' + Round(latlon[1], 6);

return result;