Here are some images from this morning's walk around Peebles Island with a Canon EOS RP and the RF 600mm f/11 IS STM lens. I'm satisfied with the image quality of this bargain lens compared to some other options I've had for that kind of focal length. And the fact that it's relatively small and light doesn't hurt.
The higher ISO quality of full frame sensors, the ability of the mirrorless cameras to focus well with darker lenses and a very effective five stop image stabilization is what makes this lens feasible. These and a few more from today can be seen at https://trulandphotography.com/peeblesisland.