Only real use ive found for an old android phone was using it as a backup alarm clock. Surprisingly kind of hard to find alarm clocks that are as good as ones on a phone.

Another good use could be gaming handheld for emulators.

Emergency backup phone thats charged up in your car? Idk dude with the way phones are locked down and the difference across them, hard to really have any use afted security updates end uness you wanna patch your own kernal.