This tool tells you if your console is vulnerable to fusee-gelee. Check out the tool here.
Yes, I'm aware that all consoles can enter RCM, so this site should be called "Can I fusee-gelee?" but that doesn't roll off the tongue, you know?
This tool is heavily (and I mean heavily) based on the .ssnc command from the Discord bot Kurisu.
Credit to Nintendo Homebrew for doing most of the hard work.