I've been looking for an iCal server to serve as a database for events. I agree with the author, this space is rather empty. Most of the projects out there have aged quite a bit and could use feature enhancements. (I.e. annoymous RSVPs, flexible notification perefences on a per user basis)
I was looking at bedework, however it doesn't deploy very easily. Now I'm looking at Radicale. It does have a docker container, but it's not well documented.