Disable Turbo Boost to Reduce Power Consumption and Heat
The thing is if your laptop cpu is getting really hot and you are trying to undervolt it then chances are 99% that there are no method to do so. I have also tried to do undervolt my Ryzen 7 5800H but no luck. Because the bios doesn't allow that much control over the cpu. I don't know the specific reasons for the manufactures to restrict such a great thing. But with this you can disable the Turbo Boost. While this might sounds stupid but trust me you won't see a massive difference in performance after turned it off.