Canon has released EOS R5 Firmware Version 1.3.1. Version 1.3 was released just a few weeks ago. Version 1.3.1 fixes an issue that was found in firmware version 1.3.
So what was the issue? Well, users were finding that the viewfinder and monitor images were being displayed too brightly when View Assist was set to [On] when shooting with Canon Log 3. This has now been fixed with its firmware update.