AMD CPU stuck in low-speed state after system resume

I just ran into this issue as well and unplugging and plugging the power fixed it for me. I’m on Ubuntu 24.04 with Kernel 6.8.0-45. I see this has been happening for a year and people on earlier versions thought kernel updates would fix things, but that might have just been a placebo unfortunately. Good to know that it’s easy to fix when it happens though.