I'm trying to setup some analytics conversion tracking on registrations, is there a final thank-you page URL after registration is complete I can use?

I think it might be this:
index.php?app=core&module=system&controller=register&do=validate

This is when a member validates their account. Just testing it to see if the numbers look right if this is the right URL to use or not.

The "email confirmation link" is ?do=validate and redirects to main page (root domain).

The actual registration process is...

(register page)/ - landing page

(register page)/?do=validating - landing page after submission