It's a laptop from Microsoft, Surface Book 2. I run Fedora Linux and Arch Linux, both of them have this issue. Either vanilla kernel or surface kernel has the same problem.
I've tried most solution: cpupower tlp thermald throttled power-profiles-daemon intel-pstate s-tui turbostat disable SecureBoot I still cannot get it working.
The CPU is not hot, neither power throttling. I can get it up to 4.2GHz, 35W package on Windows with Throttlestop These digits are What I've never seen on Linux.
It always stays below 2.1GHz, 1.3GHz when all core are stressed, always below 55C. I've made sure, TurboBoost is on.
I've opened these post looking for similar experience, not many responds.
Book2 (15") - No CPU Turbo Boost (always below 2.0GHz)
What's the maximum CPU frequency you can get on Linux with your Surface?
This is the performance I got on Windows
This is really sad. I found almost all **Intel Kaby Lake R ** processor suffer this problem.
Intel Core i7-8550U cpu frequency drops on high loads on Ubuntu 20.04 | AskUbuntu
My previous reply was erroneus. There are reports of those processors working properly, so they probably are fully supported on linux. I suggest you keep at it.
The first response of this thread has some other things to try: https://askubuntu.com/questions/1329587/intel-core-i7-8550u-cpu-frequency-drops-on-high-loads-on-ubuntu-20-04