Radicale

Log into your system with:

ssh myusername@mydomain -p 2222

Using cursor keys, space bar and Enter key select Administrator controls and type in your password.

Select Add/Remove Apps then radicale. If you don't already have an SSL/TLS certificate for your main domain then go to the security settings and create a new Let's Encrypt cert for it. That will ensure that your calendar events have some minimal level of protection from passive surveillance.

Via F-droid install DAVdroid. Within Android Settings select Accounts then DAVdroid. Select Login with URL and user name. The URL should be https://yourmaindomainname/radicale/. Remember to include the trailing slash on the URL. If you installed Freedombone from a disk image then enter your username and the password which was shown at the start of installation. If not then the password for Radicale will be within the README file within your home directory.

In tests so far the account setup process on DAVdroid is highly unreliable. Often it will say that the CalDAV service can't be found, but eventually after a while it may magically work and the account will appear.

Now go to your calendar app and press the plus icon to add an event. You should notice that the calendar account selected is your username on the Freedombone system. Synchronisation should be automatic.