Reset old device iPhone 5S

I should point out that the purpose of this exercise is that I might give this phone to someone far needier than I am, and for whom "latest shiny" is irrelevant and telephone capability critical.

After an ultimately pointless chat with a support human, I am here.

1. IIRC, in the past, iPhone could simply be reset by reinstalling the software and re-activating the phone as a new device. I seem to recall having done this multiple times on multiple phones in the past, simply because it was the easiest way to take ownership of a device.
2. At some point, in its infinite wisdom, Apple decided to "solve" the "theft" issue by permanently tying the serial number (or IMEI maybe) of an iPhone to the Apple ID that INITIALLY activated the phone.
3. Phones that were reset/re-activated at some point in their lifespan with a different Apple ID can no longer be reset by re-installing the software, rendering EVERY device that was ever re-activated with a subsequent and different Apple ID INOPERABLE the moment that a device reset/re-install is requested.
4. The software that manages this security is designed such that it requests (and hints at) the most recent Apple ID that was used to activate the phone, rather than the now required "initial" Apple ID and rejects the request. This is not accidental, it is a software feature.

This change in process has effectively flagged every iPhone that changed hands before the new security regime and which was not explicitly disconnected from the initial activation ID as "stolen".

In my case, it is likely that the phone was originally a family member's, as I tend to inherit older models when others upgrade.

So there we have it. Apple has me flagged as a thief and I can't use my own device.

The cynic might possibly observe that Apple corporate abhors the fact that older devices exist, and this activation policy has the intent of eliminating vast numbers of used iPhones from the user base, banking on the unfortunate "thieves" buying a newer device.

On an iPhone 5S. You have got to be kidding.

In this case, it asks for MY APPLE ID and refuses to accept it. I call this an activation software error. There i not any doubt about the ID or password, and Apple clearly already knows it's mine.

FWIW: This device is not listed on FindMyIphone, despite the fact that it is connected to the internet and Apple clearly knows the device is linked to my Apple ID.

FWIW2: It's not possible to log support because the serial number on an iPhone 5S is not knowable until the OS is functional (it's not printed on the back or the SIM tray).