"The issue is that the email I entered on the iPhone 6 as an Apple id does not actually have an Apple id!"
Somewhat circular statement and despite its confusing phrasing it is likely the source of the problem. To remove Find My you need the account information that was used to set it up. If you do not have it then the choices are to try to recover it, or to ask Apple to reset the device.
Thanks for your comments but I am not sure why you can't understand this statement as I believe it's quite clear. After I cleared the original id I had to enter a new id but the phone/Apple does not appear to check if the email address you enter actually has an Apple id associated with it and doesn't need a password to enter it into the phone. I entered one of my email addresses and the phone allowed me to clear the Apple id that was common to my Iphone 13 which was what I wanted. The issue now is I cannot do anything on the phone to log into the Apple id because it doesn't exist. The phone keeps asking me to enter the password for email the email address I entered as the id but as I never created one there isn't a password!
As I mention above I can't actually create an ID online with that password as I get an error that the id is invalid. I can't clear the email address it displays - if I click the ? at the end of the password box to try to enter another email I get an error "Cannot verify identity - your action could not be completed due to a server error" every time.
None of the below solutions work as you need the id password.....which doesn't exist!
The phone is nearly 10 years old and I bought it when working for a company so although may be able to locate an old archived email do not have a copy of the receipt so don't believe I can prove purchase even though I have IMEI etc. for the bottom solution to reset the phone, which I don't mind doing as I can restore from a backup anyway.
● Read this article for disabling Find My if Activation Lock has not yet engaged --> Turn off Find My on your iPhone or other devices - Apple Support , or this one to learn how to remove Activation Lock either on the device itself or on the web --> How to remove Activation Lock - Apple Support
● Help with a lost Apple ID or password:
• For help with a forgotten Apple ID (this is likely an active email address or one used in the past), click here --> If you forgot your Apple ID - Apple Support
• For help with a forgotten Apple ID password, click here --> If you forgot your Apple ID password - Apple Support
● Reset device if you can prove to Apple's satisfaction you are the owner:
Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. This is done online* at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not provide many details in the article as to what is acceptable proof. Prior to this official service Apple typically required the original receipt** issued by Apple or an Apple Authorized Reseller and documented provenance (so typically it would be the first owner who does this, or a descendant with legal proof of ownership transfer). Note that while this will let you get use of the device again, it will not help you with lost access to an account.
* There is a special link for this service. To save time you should use it instead of https://getsupport.apple.com/
**Apple recommends you keep your receipt after you buy an Apple device. --> Keep your receipt after you buy an Apple device - Apple Support
