I am using a ASrock DeskMini with AMD CPU as my main PC, and typing this post on it. But, unless your needs are very limited, it's not meant to be a NAS system.
As for AMD CPUs not being recommended for TrueNAS, yes that was the case a few years ago. FreeBSD has less support for AMD CPUs than Intel. Further, years ago people wanted to use the absolute lowest end AMD SoCs which would not even perform as well as a Raspberry Pi.
Today with newer AMD CPUs, in the desktop line, (Ryzen), embedded server line, (Epyc & Ryzen), and full server line, (Epyc), it's a different story.
My new NAS is going to have a full Epyc, (not embedded), though it's a more modest configuration than it could be. Just need a round toit before I can finish the build.