Ok, so I went to Samyang's page and got the optical drawings for the new RF mount lens, and for the Sony E lens. It's weird - they're the same, but different. They changed the color coding for the different types of glass, so that can throw you off if you don't pay attention. The only real difference I see is that the RF version has one element with "HR" glass. (Samyang calls it "high reflective" though that seems to me to NOT be what you would want - maybe the translation was botched, and it should be "high refractive", but what do I know).
The RF first, then the Sony E mount.
I guess we wait and see what comes when the lens hits the streets...