As mentioned before, /e/OS Android 15 community is available for manual install for FP3 users who want to strongly prioritise getting security updates right now … /e/OS community FP3 download
Of course community is not 100% the same as official (else it wouldn’t exist), and the manual install is not as convenient, and once official caught up to newer Android, community will most likely be phased out … but it’s out there, and it gets security updates.
Just mentioning for fellow FP3 users reading along.