[bsorbo]

Also worth calling out that the even older (2014) iPad Air 2 will be supported by iPadOS 15. It is the lone A8-series device with 2 GB of Ram.

[my123]

For the A8 gen:

iPad mini 4 is A8 with 2GB of RAM and remains supported. iPad Air 2 is A8X (with 2GB of RAM) too and remains supported. Other devices to remain supported are Apple TV HD (A8 with 2GB of RAM) and HomePod (A8 + 1GB RAM, but no big UI to deal with).

Unsupported A8 devices:

iPod Touch 6, iPhone 6/6 Plus, both because of RAM size