Is it permissible to file a legal complaint against an uncle for refusing to divide the inheritance, exploiting it, and perhaps fraudulently selling it?

There is no harm in referring the matter of the uncle to the court to compel him to distribute the inheritance to its rightful beneficiaries according to Islamic law. This is because a child may take their father to court if they have a right that the father is withholding, and this is not considered an act of disobedience (uquq). If it is permissible to refer a matter concerning a father to the court, then it is even more permissible to do so concerning an uncle.