Is it permissible to take unclaimed goods left at customs, which their owners have not claimed, for personal use or to give to the needy, knowing that their fate would be the trash?

If it is possible to contact the owner of the goods, then this must be done. Otherwise, it is forbidden to destroy or discard them because they are property. They must be preserved and spent on charitable causes and for the general welfare of Muslims or for the poor and needy, because withholding them without knowing their owner is like destroying them.