I wanted a simple bumper-style case for my iPad Mini, mostly to make it easier to hold, but wasn't happy with any of the commercial cases I could find. First attempt made solely of TPU was not satisfactory because it was too flimsy, especially around the holes, and required a C-shaped profile with top lip that was difficult to support satisfactorily.

So I made this design, with two parts: a somewhat stiff PLA skeleton, and a TPU skin. This provides sufficient rigidity and support around the holes, but still has a soft, grippable surface.  There is no upper lip, but rather the iPad sits in the frame, held in place by the pressure and friction of the soft skin. This also has the advantage that it's not difficult to insert the iPad into and remove it from the case. 

The cutaway view shows the skeleton (blue) inside the skin (gray). Note also the extra support that skeleton provides around the holes to keep them from collapsing.

The holes are sloped to provide easy access to the buttons. This also allows the case to be printed entirely without supports, for a very clean print.

I have successfully printed this on the Prusa XL using SpiderFlex matte black TPU for a nice soft surface, and Overture matte black PLA for the semi-rigid skeleton, 0.6 mm nozzle, stock generic PLA and FLEX Prusaslicer profiles. The surface finishes and color match well so the two materials are visually indistinguishable, for example around the holes where the skeleton shows through because of the way it supports the holes.