We used to have the post URL at the bottom of the details in the .ics / Google calendar export - this was introduced as a feature here:
https://github.com/discourse/discourse-calendar/pull/549
This was fabulous, as it
- Made it obvious that the origin of the Calendar entry was the Discourse instance
- Gave a rapid path to the Event post
It must have fallen off as a regression when the event Location/Description was improved last year.