Lightroom Classic won’t import more than ~20 images before Canon R5 disconnects

Problems with cables, connectors, and USB-hubs can also cause interruptions.
If it happens on both Win and Mac, there may be something wrong with the cable or camera.

It seems pretty certain it's a camera issue, not a Lightroom issue. I have an R5 also, but I never try to import directly from the camera (any camera, not just the R5). I would always advise users to import from memory card, not direct from camera, as in my opinion it's safer and LrC can be buggy when importing directly from camera.

I'd also suggest you cancel the order for the CF Express reader, as there's an issue with those cards which appear to the OS as a removable hard drive, not a memory card. The consequence of that is that LrC during import allows the use of the ADD import option (it defaults to that as well, so if you're not alive to that it means that after import your newly imported images will be flagged as missing when you eject the CF Express card). I'd already bought a CF Express card reader at the same time as the R5, it now sits unused in a cupboard gathering dust....I now always import from the SD card (I have a built-in SD reader on my desktop computer), which although being a bit slower is I think by far the safest method of importing from an R5.

This isn't a problem with Lightroom or any other Adobe software.

Please contact Canon or post this question/issue in appropirates forums.