No idea if it’s a temporary glitch or intentional, but iPadOS 14.8 is no longer being signed for some older models. This means it’s no longer possible to downgrade from iPadOS 15.
On some models it only affects the WiFi models. Cellular models can still be downgraded. On other iPads it’s both models.
The affected iPads are:
* iPad 2017
* iPad 2018
* iPad 2019
* iPad 2020
* iPad mini 4
* iPad mini 5
* iPad Air 2
* iPad Air 3
* iPad Pro 1
* iPad Pro 2
* iPad Pro 3
Edit: it has spread to more models. Some I checked a few minutes ago and 14.8 was still being signed, and now it isn’t.
The affected iPads are:
* iPad 2017
* iPad 2018
* iPad 2019
* iPad 2020
* iPad mini 4
* iPad mini 5
* iPad Air 2
* iPad Air 3
* iPad Pro 1
* iPad Pro 2
* iPad Pro 3
Edit: it has spread to more models. Some I checked a few minutes ago and 14.8 was still being signed, and now it isn’t.