How do I enable Middle Mouse Button with no 3rd party apps?

A far as I can tell from such limited information, the answer is "you can't." Hopefully we can make more progress when you follow up with more details....like what Apple device and OS version? What App needs the third button? You have us guessing and we are far too old to be good at that!

This forum section, although you cannot tell from Apple's non-intuitive label, is for Apple products made before 1998. Few people see posts here.

If you tell us your OS version, we can get you moved to a more active forum. Posting questions about modern Apple gear here is like posting a "lost dog" flyer in a sewer pipe. Only the plumber sees it.

but by the way you answered it,

Not sure what that means but I tried to be as truthful as possible. Everyone who answers here is a fellow end users like you, not an Apple employee. I have never agreed with everything Apple does but, for my needs, it beats the alternative.