The folks at Kolari Vision have been working hard on trying to solve the Canon EOS R5 overheating issues for a while now. They were the first to tear open the EOS R6 and publish what they saw. They also identified the timer that was causing the camera to shut down at the predetermined times with the original firmware.
When Canon updated the EOS R5 firmware, though, it now seemed to be looking at the actual temperature rather than using a timer – which opened up the possibilities for cooling. Matt Perks had a go at it quite successfully, but now Kolari Vision has also solved it, with a passive cooling mod. But, it costs $399 to them implement it and it will almost certainly void your warranty.