WHAT TO DO WITH MY OLD IPAD

A system software update will not, of itself, make your iPad obsolete. A device only becomes obsolete when support and/or system software updates cease to be available. You should always keep your iPad updated to the most recent version of iOS/iPadOS that is supported by your model; updates include both functional fixes and essential security updates.

The model number that you quote corresponds with an iPad Air2 - which is compatible with the current version of iPadOS. At the time of writing, this is iPadOS 15.5. Apple have indicated, however, that the iPad Air2 will not support the next major version - iPadOS16 - when it is released later this year.

iPadOS 16 Preview - Apple

You are very welcome.

At least you now know that while your iPad Air2 continues to support iPadOS 15.x, unless Apple changes the minimum system requirements for iPadOS 16.x, the Air2 does appear to be in its “twilight” period of update support…

How does updating a device which is compatible with an update make it “obsolete”? And if the device is not compatible with an iOS or iPadOS update, it simply cannot be updated to begin with.