Is it permissible to dispose of computer devices that have been left for more than two years and whose owners have not contacted to retrieve them, knowing that most of these devices cannot be repaired, or their repair is more expensive than their value, or they are useless even as spare parts?

These devices whose owners are unknown take the ruling of a found item (luqatah) and are treated as such, but only if they have value. If they do not have value, there is no objection to benefiting from them, and the criterion for value is the prevailing custom. As for devices whose owners are known, they must be returned to them.