Recommended method is run the service as non-root and non-reserved (over 1000). The radicale documents aren’t the best, but CalDAV and CarDAV aren’t the simplest standards to implement, nor do any of the big (ms, gmail) follow the correctly anyway.

For example, you have to manipulate an address book exported from Google before it can be imported into Radicale.

I don’t blame the dev, though. They are pretty much a one-man show and although radicale is a connector service you don’t interact with much, it’s crazy complicated.