A phone with Find My set on it most definitely has an Apple Account signed in on it.
Your options depend upon whether or not you care about the account. Refer to How to remove Activation Lock - Apple Support for the various ways to remove an Activation Lock.
Your first option is to recover use of the account so you can sign out on the iPhone. If your account has been disabled for “security reasons” the solution is to reset your password as outlined in this document: If you forgot your Apple Account password - Apple Support
If you find you can’t sign in, reset your password, or receive verification codes, you can request account recovery (read this support article: How to use account recovery when you can’t reset your Apple Account password - Apple Support ) to regain access to your account. More detail in —> Activation Lockout Issues - Apple Community For additional assistance from Apple Security, read: Contact Apple Support - Apple Support
If you do not care about the account but do have Apple-acceptable proof of ownership, you can request activation lock reset. Check the requirements and steps at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” Apple may typically require the original receipt* issued by Apple or an Apple Authorized Reseller. If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.
*Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support
If you cannot get the device unlocked then read this section from the very bottom of Apple Trade In - Apple :
"Does Apple offer recycling?
Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."