Looking at the Canon Australia download site, I can see that for Mac v12 there is a link to Firmware 1.6.0 which should be the latest version HERE and should be the same as the US one. Can you please check and see if that works?
When you access the page, scroll to the bottom and select the Download button.
This will create a file that you then have to expand within your Operating System, and that will create a PDF file to explain how to proceed and the FIR file that you copy to the SD card of your camera.
NOTES: you should make sure your battery is fully charged and that you have a clean SD card before proceeding.
Try this link, it's the Australian site but should still work fine. HERE
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.