iMac 5к BigSur 11.7.10 does not open .CR3 files from Canon R8 camera

As for macOS – sometimes when Apple's Raw support libraries do not support a particular format, but the Adobe Digital Negative Converter does, you can use the Digital Negative Converter to prepare .DNG versions of the Raw files that macOS can use.

Unfortunately, Adobe's policy of supporting only "the most recent three" versions of macOS now extends to the Digital Negative Converter itself. It's not "merely" that Adobe has stopped updating the versions of it that run on Big Sur – they've pulled those versions, so you can't even download them any more.

This is ironic considering that the Digital Negative Converter is supposedly how Adobe supports customers who have older versions of Photoshop and Lightroom that cannot more directly handle newer Raw formats.

Servant of Cats wrote:

Unfortunately, Adobe's policy of supporting only "the most recent three" versions of macOS now extends to the Digital Negative Converter itself. It's not "merely" that Adobe has stopped updating the versions of it that run on Big Sur – they've pulled those versions, so you can't even download them any more.

This is ironic considering that the Digital Negative Converter is supposedly how Adobe supports customers who have older versions of Photoshop and Lightroom that cannot more directly handle newer Raw formats.

Yes.

https://exiftool.org/forum/index.php?topic=17259.msg92486#msg92486

We asked camera companies why their RAW formats are all different and confusing:

https://www.theverge.com/tech/640119/camera-raw-spec-format-explained-adobe-dng-canon-nikon-sony-fujifilm

Adobe does not use Apple's built-in Raw support library. They use their own Raw support code. Photoshop and Photoshop Elements use a copy of this code located in the Camera Raw plug-in. All of the variants of Lightroom, and the Adobe Digital Negative Converter, have this code hard-wired in.

Adobe – Cameras supported by Camera Raw

For the EOS R8, it appears that

• A camera matching profile is available
• The minimum Camera Raw plug-in version is 15.2
• The minimum Lightroom (cloud) version is 6.2
• The minimum Lightroom Classic version is 12.2
• There is no support for these files in any one-time purchase version of Lightroom

So the question would be – are you running Camera Raw 15.2 or later, and a version of Photoshop which supports that version of Camera Raw? If not, that's the problem. If you are, and you are still having problems with EOS R8 CR3 files, that would be a Support issue to raise with Adobe.

Adobe – Camera Raw-compatible Adobe applications

FWIW, a Canon R8 is not supported by Big Sur.

See: Digital camera RAW formats supported by iOS 14, iPadOS 14, and macOS Big Sur - Apple Support

Or the alternative of extracting the JPG image (with all inherent metadata) from the original RAW image. I have a working shell script that uses ExifTool to achieve that extraction.