I mostly know the western, European ones but I would say 20-ish. But most of them are variations on the same basic joints.

And I only really know the furniture stuff. With half-timber house framing there are a whole lot of variations that I'm only loosely familiar with.

And then if you get into east-asian (or other regional) joinery there's amazing worlds of cool stuff using very different techniques, meant for use with different kinds of local wood applied to other systems of living. There are some good books and videos about japanese joinery but I'm also very curious if there's stuff on other regional styles.

Looks like an exotic alternative spin on a slip joint. Pretty nice!

I will have to try that too.