I have since upgraded to Monterrey and I confirm you can't preview your raw files anymore within Aperture.I haven't, but from what I've been told :
There are big bugs on M1. Basically making it unusable.
On Intel, Aperture is working BUT it won't preview RAW picture anymore (Raw images that used to be visible under Big Sur) ...which renders it almost useless if you used to shoot Raw images.
You can still switch to Jpeg if you happened to have shot in Raw+jpeg, and preview the jpeg. You can view the raw file in the finder. By the way, there used to be a difference in finder when viewing jpeg and raw. Not anymore. Seems that Apple has decided to render raw as jpegs :-(