Is it possible to implement Discord Rich Presence into BYOND games?
You wish lol
It looks like you should be able to, yeah.

If you compile athe discord SDK and make it available to your game through a *.dll file, you should be able to execute it using,
call("your_dll.dll", "dll_func_name")(args)

Just a thought.
It IS possible. And it's not hard. If you know some PHP, and have an apache server, you can use World.Export() to make it all happen.