Is there a way to display UV distortion in the Viewport as a heatmap, like one can do in Modo? It's NOT a duplicate of another question, which was about showing distortion not in the Viewport, but in the UV Editor instead.
If you insist:
No, unfortunately there is currently no functionality to show the distortion of UV maps in the 3D Viewport as heat maps, like one can do in Modo. The question Is there a way to show distribution of UVs as a heat map? seems to cover all the options for displaying UV stretch in Blender.
But this seems like something that might be possible to code in Python as an add-on, maybe it would not be very difficult to output this information as vertex paint information. Who knows?.. maybe someone will see this question as a fun Python exercise...