Facebook only documents exporting a calendar file. (In the mobile app there's a simpler way to add a single Event to a system calendar.)
I couldn't even find any mention online of the Facebook calendar feed. Just sad comments on Facebook's removal of RSS feeds about 7 years ago.
I was just about to give up when a last search found a Business Insider article from Dec 2019. Some Facebook dev has kept it alive in the most obscure location possible.
You can't find it by looking your Facebook Calendar: https://www.facebook.com/events/calendar
You can't see it by looking at your Facebook Events: https://www.facebook.com/events/
The only way to find them is to use the web UI and inspect the ... context menu for any single Event.
Beneath that you will see "Export Event":
In fact the resulting dialog, in addition to allowing saving of a single event, also provides the secret URL for a Calendar feed (RSS, iCal) including the Facebook UID and a "key" for access:
In Google Calendar web here's where that URL goes:
It can take hours for the feed content to appear and updates are likewise slow to show.
PS. I do appreciate so many Facebook page URLs are readable, persistent, and meaningful. I rely on that given the ever changing menu and navigation structures.