7Artisans has announced a 4mm f/2.8 circular fisheye in the EF-M mount. There is currently no RF mount version of the lens for the EOS R7 and EOS R10.
About the 7Artisans 4mm f/2.8 Circular Fisheye
Featuring a one-of-a-kind 225° field of view, 7artisans 4mm f/2.8 fisheye lens can create a circular fisheye perspective on Micro Four Thirds (M43) & APS-C cameras. Photographers can create a 360° full panorama image with a minimum of 2-3 shots. The lens weight only 7.09 oz (201g) which makes it extremely portable and allows photographers to have creative shots anywhere, anytime. The lens can also be mounted on DJI Inspire X5 cameras for creating a unique perspective you have never seen before.
7Artisans EF-M 4mm f/2.8 Circular Fisheye $149
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In contrast EF-M lenses from the M line of interchangeable-lens mirrorless cameras had a film-to-flange distance of I think 16mm, anyway, shorter than the RF. You can't really make an adapter that lets you mount the lens closer than the RF flange as it'd have to "reach into" the RF camera bodies. That's not a technical impossibility but the entire lens would have to stick into the RF body and while the mount is big, I'm sure it's too small to allow any EF-M lens to be sunk into the body, and therefore such an adapter couldn't be made.