If the encryption option isn’t shown by default in one of the automatic partitioning options you can always manually partition and choose to encrypt the newly created partition.
Important: There is a slight error in one of our configuration files that might lead to a non booting system though it is installed with full disk encryption correctly.
So if you like to manually encrypt your system, please before starting the installer edit the file /etc/calamares/settings.conf and add
right after the virtualbox in line 36. You need root rights to edit this file.