Definitely picking Renew and not upgrade. I verified that the license is Self-Managed and not Hosted. Just wanted to make sure I wasn't doing something goofy or missing a step.
I'd like to think 3CX would put a notice on the renewal page if they're going to grey out the "Hosted" checkbox, like, "If you're sure this is a Self-Managed instance, please click here to submit a request to have the Hosted option removed," or something to that effect.
Also, for us lowly Bronze partners, I'd hate to have to burn a support request on something we don't have any control over, yet absolutely necessary for continued use of the service... But maybe we'll save that for another post!