Android version upgrades via the updater (so-called OTA upgrades) need to be specially prepared and tested by the development team.
You can follow proceedings by checking the weekly posts in Topics tagged development-updates , respectively section “OS OTA Related information”.
You will have to wait until an OTA upgrade for FP3 to Android 14 (U) pops up there under “Completed”.
Note that even if an OTA upgrade is being prepared, it will only be for stable/official builds. In case you are on dev/community builds, upgrading will have to be done manually and you don’t need to bother waiting for an OTA upgrade.
Here’s how to find out whether you are on stable/official or not … [HOWTO] Give complete /e/OS version info easily for support, answers, comparison etc