According to what Adobe says at the link that you have included, Lightroom Classic will not support photos and videos captured in the HEIF format unless they were shot with iOS devices. I saw nothing about HEIF photos and videos shot with any Canon cameras:You are correct, apologies for having forgotten about that, definitely something to pursue if you are one of the lucky ones (it is only available on the EOS 1D X Mk3, R5, R6 and R3, and I'm going to guess it will not be retroactively implemented on older camera bodies like my RPs). Apparently it requires the DIGIC X processor used by these more recent high-end cameras. Adobe's website mentions HEIF, so there is a chance it is supported https://helpx.adobe.com/lightroom-cc/kb/heic-files-support.html It is interesting that Canon went along with a format standard that is vendor-defined (Apple, 2017), instead of trying to revive industry consortia initiatives e.g. JPEG2000 to address the issue of better bit depth. To Apple's credit, HEIF not only adds 2 bits (and apparently allows for more as a format), it also has a more efficient compression such that the resulting file is approximately the same size as an 8-bit JPG. Setting your camera to use HEIF is somewhere in the HDR menus, I do not have a manual for any of the supported cameras so you will need to sit down and look through the user manual to get the details. Sony seems to have also implemented HEIF, less clear about Nikon. Most computer browsers do not support it (yet).
"Although modern camera devices provide the capability to capture HEIF/.heic photos and HEVC (H.265) videos, Lightroom and Camera raw support only HEIF/.heic files created with iOS devices."