After a lot of trial and error I finally identified the source of this weird problem, at least on two Ryzen (3500u and 2500u) laptops
When any Ryzen laptop is powered on and charging, and the battery is below a certain level (usually 50% or less) and you start any kind of high demanding cpu app like a game or maybe compressing a file, the laptop BIOS and motherboard power control unit will send the PROCHOT EXT signal to the CPU, locking its speed to the lowest possible (Usually around 400mhz). This seems to be a failsafe mechanism so you cant exceed the max allowed power consumption that the AC-Adapter or the Motherboard itself can handle.
My OEM HP laptop Ac- power adapter is just a mere 45w unit, using power hungry apps like gaming can raise the CPU well above its rated wattage, for example. my Ryzen 3500u has a rated wattage of 15w, but it can go as far as 23W while gaming or compressing files (you can check that using hwinfo in your own laptop).
23W is about half the power the ac adapter can give to the entire laptop. charging the battery can use as much as 20w so you can hit the 45W limit very easily and the laptop bios/motherboard will lock the cpu speed temporarily, until you reach at least a 70% battery charge.
Restarting the laptop will kinda "fix" this issue, but as soon as you combine high cpu usage + charging the CPU speed WILL drop again until charging stops or you reach a certain level considered safe by the motherboard firmware.
Thats why some people claim that uninstalling drivers, programs or devices, will "fix" the problem, because uninstalling any driver o device implies restarting the system, and by the time you finally restart the laptop after messing with it for a few hours the battery is finally charged.
The same "fix" applies when someone wipes out an reinstall windows trying to solve this problem, by the time you finally reinstall windows, drivers and programs the battery will be totally charged and the problem will not appear... you guessed it: until you charge the laptop and do any cpu demanding task, even for a few seconds.
Selling laptops with weak-cheaply made power adapters seems to be pretty common these days. Almost any recent laptop will exhibit this behavior when power stressed.
Kinda miss the good old days with those Brick-like 150W power adapters that were overkill for almost any laptop, nowadays you cannot use the laptop full potential if your battery is not fully charged and the moon is on the right phase. *sighs*
