trying out #Blender 4.5 LTS. Now includes a built in '.OBJ import' geometry node.
Found a quick way to fix my DEM-derived meshes, to get rid of lakes - or lochs, this one is Scotland :)
Before, I'd go into edit mode, select a flat face, select-similar with a normal difference of 0, and delete the faces
This geometry nodes setup does the same thing, but faster and non-destructively.
Comparison is really dot-product equals 1 (or > .999999)