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.
Disable Turbo Boost to Reduce Power Consumption and Heat