Here to report also seeing this behavior. Using the web client on Linux machine (PopOS, Ubuntu essentially) and Firefox (Mozilla Firefox 84.0.2). When I go to the login page the dialog for my username is fine. I enter that info and instead of the next box appearing asking for my password, it takes me to a blank page. The html for that page is literally just
<html>
<head></head>
<body></body>
</html>
Sometimes if I try it enough times in a row I'll eventually get to log in. I just used Chrome on the same machine to login and it worked the first time. Also tried it with the Brave browser and that also worked fine.