My experience with iPads losing Apple support is every app just shows you an error message saying your app is out of date and can't be used, while the app store won't let you update it because the latest api version doesn't support your device. Unless you are using all FOSS software, most apps want to connect to some server, and that connection breaks rapidly without updates.

If you can load Linux on it it's still usable, but Apple OSs degrade rapidly after Apple stops supporting them. Apple is better about keeping devices on the latest OS version, but much worse about support after that period.