Unable to contact original owner of an iPhone - How to reset a found iPhone

A previous tennant has left a box full of devices in their storage. After multiple attempts to contact them they didn't reply nor did they pick up their belongings. The current tennant of the appartment to which the storage belongs was given permission by landlord to give away the box and items.

In this box I found an iPhone 6s plus.

I tried resetting it through iTunes but now it's asking to log in on the Apple ID connected to this device.. Which I obviously don't know the information to.

If I go to an Apple Store or aMac would they be able to reset this phone without the info to the Apple ID?

[Re-Titled by Moderator]