Is it permissible to pay the value of an electronic device that cannot be returned, and donate its price to the poor or place it in the mosque with the intention of its owner?

You must search for the owner of the device to return it to him. If you are unable to find him after making an effort and have despaired of locating him, then give its value in charity on his behalf. If you find him later, give him the choice between approving the charity and receiving its reward, or that you return the value of the device to him and the charity becomes yours. It is permissible to take ownership of the device while giving out its value if the owner cannot be reached.