Apple publishes iOS and iPadOS 16 adoption rates on Developer website.
According to Apple, iOS 16 is now installed on 81% of modern devices and 72% of all compatible devices. iOS 15 is installed on 15% and 20% respectively.
iPadOS 16 is running on 53% of modern devices and 50% overall. iPadOS 15 powers 39% modern and 37% of all compatible iPads.
These numbers show that projects targeting iPad still need to consider supporting previous major iPadOS releases.
Apple Developer Support: App Store
Developer:Adjust supported iOS and iPadOS releases accordingly.
QA engineer:Keep iPad devices running iPadOS 15 and, possibly, iPadOS 14 for proper on-device testing.
PM/DM:Adjust supported iOS and iPadOS releases accordingly.