I checked this, Andreas, and CR3 is present in the list in the RT build I refer to above. The images also load and show the embedded JPG from the camera as thumbnails, but when I load them to edit the image is white and says ‘Exif data not found’ or something like that in the corner. For now, I convert to DNG first suing Adobe DNG Converter to circumvent that problem.
Looking forward to a new dev build, @HIRAM! Thanks for your efforts, and let me know if I can help testing for future OSX versions of RT. Have been trying out some trial versions of commercial suppliers like Capture Pro recently, and it really makes me appreciate RT and its excellent tools in Lab space so much more!!