edit 2: Selecting 'use mobile data' when downloading and installing does work. Go to Settings > General > iPhone Storage and delete the update package. Restart the download & install process and let it use mobile data this time.
I get the feeling checking the hash does work over LTE as opposed to Wi-Fi, based on absolutely wild speculation.
edit: MacOS reports iPhone being up to date.
edit 2: Selecting 'use mobile data' when downloading and installing does work. Go to Settings > General > iPhone Storage and delete the update package. Restart the download & install process and let it use mobile data this time.
I get the feeling checking the hash does work over LTE as opposed to Wi-Fi, based on absolutely wild speculation.