I currently use fruux (which is proprietary) to synchronise my to-do lists and calendars. However, I was wondering if there was a FOSS CalDAV service which I could use for free.

I have already looked into Nextcloud, and I don't believe it is what I'm looking for. I also don't want to use ProtonCalendar or Tutanota Calendar, as they only work with their own respective apps.

In a nutshell, I would like a service that:

• Supports CalDAV
• Is free (as in free beer)
• Supports both calendars and to-do lists

EDIT: I am able to self-host some apps using Render, but they must be compatible.