Hey if you're interested in something more to report about the KB5121003 update, it also broke charging management on several 10th gen (the current gen) Lenovo Legion laptops, and this is not the kind of problem you'd hear very often lol. Specifically it seems to break Lenovo ACPI-compliant Virtual Charge Controller driver on those Lenovo laptops, which makes the laptop randomly thinks the AC charger gets disconnected (with corresponding power limits for battery power kicking in), even when it isn't and the physical charging LED still behaving normally.

There is a Reddit post on this with additional details (though unfortunately I cannot post a link here), as well as on Lenovo Legion Discord channel. This has been affecting dozens of people now, even with these very high end laptops.