Currently there are 11 native Telephoto Prime lenses for Canon R3 and 10 of these lenses are autofocus (AF) type.
R3 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on R3.
Since Canon R3 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 9 Telephoto Prime lenses with Weather Sealings.