calendar servers?

[Ian Malone]

I've got a project I'm developing for the raspberry pi which requires
a calendar server. While it will probably run on raspbian it would be
handy if I could do some of the work on Fedora. Is radicale the only
calendar server? It's the only one that shows up in a DNF search. They
have a pretty webpage, but I'm a little put off by their "Development
choices: lazy" thing, such as, "The Radicale Server assumes that the
clients are perfect and that protocol violations do not exist."
Under raspbian there's the Darwin Calendar server (calendarserver)
though that has it's own problems in lacking TLS support.