Downloading and installing a Netflix IPA on iOS 15 is generally used to run the app on devices that no longer support the latest official version or to use "tweaked" versions.
: Modified interfaces or performance modifications created by third-party developers. Prerequisites for iOS 15 Sideloading netflix ipa ios 15
It says Netflix not compatible with my iPad Air 2 on iOS 15.8.1 Downloading and installing a Netflix IPA on iOS