Update: I've added a new model for printing which fixes the wrong counterbore holes (recommended by  MG-Grafik-Design - many thanks!)
This new model is not tested on a real Zwift Ride (since I don't have one atm)! But I assume it will fit since it is almost identical to the former model. The new model is for the long screws as well. If someone may provide the length of the screws included in the bundle I might create a version for the bundle frame as well.

loosely based on a design for the Wahoo smart trainer rocker stands I've found somewhere else (can't remember where)

It uses the long screws from the additional feed delivered with the Zwift Ride (you have to remove the little rubber sealing/ring with some sort of tweezers or so in order to remove the screws)
Update: I've learned that the longer screws are included only in the stand alone version of the Zwift Ride, not when you buy this as a bundle including the Wahoo Kickr. The screws from the bundle are too short and won't fit. But if you are able to get some screws with a length of 75 mm it should work as well.

printed with 0.8 mm nozzle and PETG at 0.55 mm layer height, 3 walls, 3 layers top and bottom and 40 % gyroid infill.

some support added to the overhang of the adapter, it might help to support the outer part as well, as shown in the print preview picture
minimal tree support works fine too if not even better