I was looking at the paper circuits in Osmond and it took me a little bit but I’ve been able to import the gerbers into kiCAD. One useful tip is to make sure to have the right extensions the various board layers

You want to select the board outline, which I’ve found is usually on layer one and cut and paste it onto aux 1. output extension .gm1 so it’s recognized as an edge.cut file
One thing people have pointed out is most of the Osmond layouts are single sided, which many board houses have a minimum 2 layer design rules. You can just duplicate layer 1, and mask 1 and rename them layer 2, mask 2 and add the proper extensions