I am trying to calculate the flowpath distance between two lat lon points in qgis, and can't figure out a simple solution. I have many lat lon points of the centers of wildfires, and I want to calculate the flowpath distance from these points to a water quality site. Ideally, I would be able to do this in the field calculator, but it is also fine if it is outside of the field calculator. I'm working in the most recent version of qGIS (3.28.3).
I've looked at r.flow in GRASS and Flow Path Length in SAGA, but these don't seem to work for the flowpath distance between two points.