“…The second issue poses an actual problem though. In a recent work [Hei21], one of the authors has shown that in some cases an extension operator U ε,• : W 1,p (Q ε ) → W 1,r (Q), 1 ≤ r < p, can be constructed for some geometries including the Boolean model (strictly speaking this was shown for an extension from the balls to the complement in the percolation case). However, [Hei21] also suggests that the Boolean model for the Poisson point process requires p > 2 for U ε,• to be properly defined for some r > 0.…”