Update
I have more than enough storage to update my phone & it’s still not letting me update it .
iPhone XR, iOS 15
60.9 GB of 64 GB and things are still calculating. For all practical purposes, you are maxed out.
Message says you need 1.31 GB of available storage......but.....the update itself is another 3 GB or so and even more space is required for overhead.
Try updating by connecting the phone to a Mac. Then, start deleting data big time.