We have templates for both male and female pairs of the RF mount. They fit my camera and lenses without further modification.
Having done this, I belive it is possible to have a mount that fits both RF and EF - you just have to cut a bit extra away.
Extension tube still a longer-term plan for this project but as most RF lenses seem to need electronics to focus etc then I'm not sure of the point unless the contacts can also be included.
Still, this might be a starting point for someone to make something useful! Let me know!

Creality

Ender 3

Yes

Yes

0.2

100%