This is just a fancy UI on top of CalDAV. You have probably seen CalDAV in action at work with Microsoft’s god awful version of it (via Exchange Server or MS36

This is just a fancy UI on top of CalDAV. You have probably seen CalDAV in action at work with Microsoft’s god awful version of it (via Exchange Server or MS365 or w/e they call it); or Google Workspace or Google Calendar invites. Across domains, it tends to be a hit or miss (due to proprietary EEE bs) but within the same organizations/domain it works decently enough. Even works well beyond the 100 person limit in “Apple Invites” Sigh, why do we keep re-creating the wheel.