Bill Claff, over at Photons to Photos – probably the best independent data source for relative camera dynamic range – measured the Canon R6 and determined that, at the normal ranges of ISOs, it beats the Sony A9 II, but comes behind the R5.
Where the R5 beats the A9 II by about a stop, the R6 is between the two, one third of a stop higher than the Sony flagship and two thirds of a stop below the Canon mirrorless flagship. Sony’s A7s II is roughly on par with the R6, and the Sony A7R IV beats the R6 in most intervals below 600 ISO. All are bested by the Panasonic S1. To play around with graphs comparing your own body, use the link.
Claff measures “photographic dynamic range,” which is number of light levels that can be captured successfully by a sensor while still having acceptable noise levels at a normal viewing distance.