Currently there are 11 native Telephoto Prime lenses for Canon R6 and 10 of these lenses are autofocus (AF) type.
R6 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on R6.
Since Canon R6 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 9 Telephoto Prime lenses with Weather Sealings.