Ok, I have recently bought Ryzen 5 5500GT. I am also trying to enable C4 and deeper states but I am unable to.
My motherboard is MSI B450M-A PRO MAX II and I have enabled "Global C-state control" and played with other bios settings like "Modern Standby" but I am unable to enable deeper C-states in my Ubuntu OS.
But it is using C3 for 99% of the time while idling and I have seen it take 3.5W CPU package power (Thanks to being APU).
I would also really love if I can make modern standby work
Edit: It seems having 3 states is correct, they are just labeled wrong according to random reddit user, lol.
Now I need to worry about the Modern standby feature