S series gets montly security updates. A series is costlier because of the software features provided, not because of software updates. You can check to update policy on samsung.com.
I'm using A71 too and I too have the security patch update for October. But I guess we'll hopefully receive the January security patch update by the EOM. And as for One UI 3.0 I don't think we'll receive that before the end of April. So stay clam and keep waiting.. ☮️