find the owner

'Activation Lock for iPhone, iPad, and iPod touch' is a security feature that's designed to prevent anyone else from using an iPhone, iPad, or iPod touch, if it's ever lost or stolen. To learn more click here --> http://support.apple.com/HT201365

For an individual to remove an activation lock absolutely requires the information for the account that applied the lock. Click on this link to learn 'How to remove Activation Lock' --> https://support.apple.com/HT201441

If you do not know the required information and you are not the original owner, get the owner of the account to remove the lock or return the device for a refund or recycle it. The device is otherwise useless to you. If the owner is unknown and has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who gave you the device knows them.

No. No to all you ask, and no to all you want to do, and no to all you will suggest here, No. Just no. Recycle it.

Since that answer never suffices…

That iPhone is indistinguishable from a lost or stolen iPhone.

Activation Lock is intended as a theft deterrent. It’s intentionally not easy to bypass.

Only the person holding the Activation Lock can remove it, or Apple.

The seller here inevitably disappears, as you would not otherwise be asking here. You’d be working with the seller, if this were a legitimate transfer: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Which means…

We cannot help you bypass Activation Lock.

Apple will not help bypass Activation Lock. Not without proof of original purchase or legal paperwork that you don’t have.

Apple will not provide info on the Apple ID holding the lock either, as that would be a disaster. If the person holding the lock wanted to display that info on the iPhone, they have the opportunity within Find My for a lost device.

In summary, that iPhone is and will be useless to you, and you will want to recycle it.

How to recycle it? Apple accepts recycling, and your local municipal government will generally also have recycling info.

More details: The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

Your ONLY option is to inquire of the individual from whom you obtained the device.