Right, the key point being it is almost impossible to reuse iPhone or iPad hardware once the updates stop coming, even though the hardware is absolutely amazing. A 2017 iPad Air is still awesome hardware if you could jam an optimized version of Android/Linux onto it.
If you don't need it to be an Air, I bought an 8th gen iPad on eBay last year for about $80 and it will let you install iOS 26, although with the 32GB model you can't fit many apps on it.
https://news.ycombinator.com/item?id=25172883