Ubuntu 24.04 LTS ships with GNOME 46. GNOME 46 is the first version of GNOME that includes this feature:
A collection of additional improvements to Online Accounts have also been made, thanks to funding from the Sovereign Tech Fund [...]:
- A new WebDAV account type has been added, providing a generic method for integrating online contacts, calendars and files into your GNOME experience.
Fastmail supports WebDav in its integrations for files, contacts and calendars. How do I enable them on Ubuntu 24.04? I've tried to go through the GNOME Online Accounts tool, but it doesn't seem to work. Maybe I'm entering the wrong information?