Well that's unfortunate but it is what it is. I'll se if I can get Ubuntu to update the package or contribute an updated version myself.
If that's not possible, I'll try to find a workaround and if I do I'll share it here.
I don't think so, we checked the server and client settings multiple...
I cant get Thunderbird nor OutlookCalDavSynchronizer to work with SOGo Webmail's CalDAV calendar on an Ubuntu 22.04 LTS server with Plesk Obsidian 18.0.55.
I tested this with Thunderbird 115.3 and Outlook 2016 + OutlookCalDavSynchronizer 4.4.1 using Windows 10.
I also tested it with Thunderbird...