Hello Simon, Disclaimer: I am nowhere near knowledgeable regarding cpu frequency scaling
Perhaps will you find tips in the official Lenovo doc to fine tune power saving under Linux for Thinksystem: https://lenovopress.com/lp0826.pdf it seems to require setup up the UEFI accordingly to use acpi-cpufreq and there is a recent amd-pstate similar to intel-pstate, which should provide the best results: https://www.phoronix.com/scan.php?page=news_item&px=AMD-PSTATE-2021
