It seems like the documentation is more excited about telling me what components Prefect Cloud has than about hardware requirements. Unfortunately, there isn't a direct mention of minimum CPU and RAM requirements for self-hosting a Prefect 2.x instance.
You might want to take a wild guess or try running it on something and see how long before it crashes. If I come across any useful information, I'll let you know. But hey, isn't trial and error what life is all about?
For the proper documentation, you can check
here.
Good luck!