On the other end of the spectrum from Robinhood's clean and modern UX, there is Interactive Brokers.
Logging into IBKR is one of the most consistently aggravating authentication experiences.
Mobile reauthentication
A single login on the mobile app is often insufficient. As you navigate through account tools, you sometimes land in embedded web views that prompt you to log in again, or even twice more.
The hellish desktop-mobile loop
The system becomes truly unworkable when moving between mobile and desktop. IBKR enforces a single active session policy across all sources.
When you attempt to log into the desktop web portal, the site naturally prompts you to complete two-factor authentication on your phone. Yet the moment you open the mobile app to authorize the request, that very act often seems to register as an active mobile session—immediately booting you out of the desktop session you were attempting to access.
The standalone IBKR Desktop app is somewhat more resilient than the browser, but it has its own shortcomings. Key destinations like account management and portfolio summaries cannot render inside the client and force you back into a web browser anyway. Even launching the browser from within the desktop app isn't foolproof—it can itself trigger another round of mobile two-factor challenges that terminates the desktop session. For a dedicated application tied directly to a physical machine, there is no reason Interactive Brokers should treat authentication like a fragile, hostile maze.