The /e/ version number does not directly relate to a major Android version.
/e/ versions are available using several Android versions as their base, see here … https://gitlab.e.foundation/e/os/releases/-/releases.
/e/ 0.18 is available using Android 7, 8, 9 or 10 depending on what’s available as a base on the device it’s running on.
On the Fairphone 3/3+ /e/ currently support Android 9 and Android 10 as their base.
Support started with Android 9, and the OTA updater which installs the regular OS updates as of now can’t upgrade the OS to a new major Android version, this is still in the works.
As long as that’s the case, /e/ are rolling out their OS updates for bases Android 9 and Android 10, and upgrading to Android 10 is a manual process, here’s how … https://doc.e.foundation/q-upgrade-fp3. If this isn’t done, the device will stay on Android 9 for now.