Apple A16

Apple's site says iOS 27 is compatible with iPad Pro 4th generation and later with an M1 processor or later.

iPad Air, 4th generation and later, M.2 processor and later, iPad, 9th generation and later, running an A16 processor, and iPad Mini, 6th generation, running an A17 Pro processor.

9to5Mac says that drops five models that can run iPadOS 26.

They include the third-generation 12.9-inch iPad Pro, the first-generation 11-inch iPad Pro, iPad Air 3, iPad Mini 5, and the eighth-generation iPad.