Hi BigBlue - Welcome to the Zoom Community.
What's likely happening is that DuckDuckGo, might be holding onto a little piece of information—a "cookie"—that tells Zoom you're already logged in. Even when you try to sign out, the browser just keeps handing this cookie back to Zoom, so it feels like you're in a never-ending loop.
I would recommend to clear cache and cookies on your Duck Duck Go browser, close and re-open the browser, and try to see if the issue persists.
If you're still experiencing the same problem, you can force sign-out the session via the Zoom Web portal (zoom.us). This is the ultimate way to make sure you're starting with a clean slate. On the Zoom Web Portal (zoom.us), go to your Profile page, scroll all the way down to the very bottom of the page, and you should see a button to sign-out per session, or sign you out of all sessions. Please see sample screenshot below.

I hope these recommendations help. 😀