Attending
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Attending is an event silo with a simple, minimal UX for publishing very nice looking event pages.
Example event:
API
It’s not clear whether they have an API or not, but their site is quite friendly it sounds like they either may have or would be open to having an API.
Perhaps reach out to creator https://twitter.com/stef to see if they have an event creation / RSVP backfeed API or would be open to creating one!