How to update to iOS 14.8.1 from 14.4 when only option is IOS 15?

Hi Community,

I have two iPhone SE (first generations), one which was on IOS 14.7, and gave me the option to update to the urgent security update 14.8.1 which I performed last week, rather than iOS 15. The second is on iOS 14.4, which I would also like to update to 14.8.1. However, for some reason, I do not have the same option to update to IOS 14.8.1 on my second iPhone SE. Instead, I am only given the option to update to IOS 15, which I don't want, as I'm on an older device and am happy with IOS 14. Why is it that two devices, of the same model, on the same IOS version, do not give me the same options to update? Why did I only get the choice on one of them? I would very much like to secure the OS on my phone by updating to IOS14.8.1 rather than IOS 15, which apple have said we will have a choice to stay on and get updates for if we are still on IOS 14. Can someone provide me with any details on how to update to IOS14.8.1, when my only provided option is IOS15, when I'm still on IOS 14?

Many thanks