Colloq

 Colloq  is a service to find and track events, used as part of IndieWebCamp Nuremberg 2018.

How to POSSE to
No known way of POSSEing automatically, though there is at least one manual POSSE example:
 * https://colloq.io/events/indiewebcamp/2018/nurnberg/1
 * original: http://indiewebcamp.com/2018/Nuremberg

Colloq's event display appears to be very "POSSE positive", as it contains a clear boxed link that says  Visit the website of the event that links back to the original event page.

IndieWeb Support
No known indieweb support yet, like no microformats2 (e.g. h-event) markup on event permalink pages (as of 2018-026).