Bookworm: Weird Firefox issue

[local10 <local10@tutanota.com>]

Hi,

Have been using Debian + Firefox with Tutanota email for a number of years and everything was fine until about a week ago when I started to get a blank empty white page when trying to access the Tutanota login page: https://mail.tutanota.com/login

Tried https://mail.tutanota.com/login in Chromium and it works as it should, that is, shows a proper log in page with the ID and password fields, no issues. Tried https://mail.tutanota.com/login in Firefox v126 but still got an empty white page.

Any ideas? Thanks

$ aptitude show firefox-esr
Package: firefox-esr                     
Version: 115.11.0esr-1~deb12u1

Operating System: Debian GNU/Linux 12
KDE Plasma Version: 5.27.5 KDE Frameworks Version: 5.103.0 Qt Version: 5.15.8
Kernel Version: 6.1.0-21-amd64 (64-bit)
Graphics Platform: X11