Hello,
You might want to take a look at this post on the Discourse forums:
It seems that you can still run Discourse in an Ember3 environment instead of Ember5 using a flag. Unfortunately, I couldn’t find more information about that flag with a quick search.
In the following post, it is confirmed that this approach currently works to restore the calendar functionality:
It might be worth trying until the Events Plugin gets updated!
Currently working with the web team on an alternative plugin, so hope to have this resolved soon.
New plugin is now installed!
Thank you, Jummivana! 
I couldn’t help but notice an influx of flying events since the new plugin. Happy flighting!
Has the calendar simply been been dropped?
The calendar is back:
I am still trying to get my previously (last week) posted flights to show up in the calendar for future (next month) flights. Is this not possible? Also, is the history of previously flown (last year) flights going to be active again so that we may refer to and use (next year) data posted for those flights?
I think you will need to edit those manually by clicking on the COG wheel in the composer, then “Create Event” then saving it.
Yes and No. It’s not saved in the Calendar anymore. You will have to check your previous posts.