On my oold Thinkpad T430 with an Intel i5-3020m (I think) CPU, Plasma supports energysaving settings through the GUI.
These are absent on my AMD Ryzen 5 3500U new Thinkpad. I actually thought the AMD support was better?
So it seems there are little tools for fixing that? I am currently trying to use RyzenAdjust but I have not tested it much.
I also made a script for simply disabling CPU cores using sudo echo 0 > "/sys/devices/system/cpu/cpu$core/online", but I heard you should rather change the governor, as disabling cores could increase the battery consumption.
Apart from that, I monitor my CPU temps, have disabled “dim screen after x minutes” and have the screen go black after 1min. Still I think batterylife is not great, and I would be curious for help.