Gregory Dudek wrote:

Is there no way to provide a workaround or option akin to my patch for those who want to support those non-compliant browsers.

Well, you can patch your instance so that all 500 errors is made into something else. I wouldn't recommend it though.

Not doing anything will assure future people like me plenty of pain and frustration. Arguably, returning a 500 error with an authentication request is questionable,

I agree with that, and I can't see any reason to do that. The standard way of displaying a login page is to send "302 Moved Temporarily" and redirect to the login page. The login page is displayed with a 200 OK.