I recently started using Brave as my browser. This is why I also started using it on my iPad. Normally I would use WhatsApp Web via requesting the desktop page. This works just fine on mobile chrome and safari. However, it is not working on Brave. I think Brave is sending an older user-agent. And this is the reason why you get this message which says you should update your browser.
Could you please update the user agent or at least give an option to set one by yourself?
Best regards Nils