As a firefighter, I wedge doors all the time during the course of the day. The original is a nice design. I like the large finger hole that can be gripped even with wet gloves, and the angle of the wedge is just right. But the wedge itself was too small. This is a new parametric design done in Freecad based on the dimensions of the finger hole and angle of the wedge.

Printed base down on a textured bed from PETG, with minimum 5 layers wall thickness and 30% infill for adequate strength and grip. Can wedge the hinge or at the floor. Dip in rubberized coating for maximum grip on smooth floors. Can stack 2 if necessary for tall thresholds.