Problem with Disroot email login and XP browsers

The only email account I ever liked was Disroot. They are 100% reliable and
there are no ads.

Never had login problems with any of the forked or backported browsers
compatible with XP. All of sudden, I'm redirected to this "outdated browser"
page.

https://mail.disroot.org/?/BadBrowser

I tried a couple of those user agent switching extensions. Changed the user agent
to the latest Firefox strings. Didn't work.

Posted at the Disroot Forum. No replies.

I have browsers like Mypal/Firefox, Basilisk/Serpent, KM-Goanna (K-Meleon), etc.

If I can't fix this problem, my Disroot email account is gone forever.