Congress can appoint a commission or a special counsel or special prosecutor. The DOJ has a number of options available as well. State AGs can get involved as issues pertain to their states.
The voting and immigration fix, along with socializing medicine and enacting the green new deal should be a focus of the administration along with cleaning the federal stables both from the Russian digital intrusion and the human waste trump land deposited throughout the federal workforce should be another.
The more truth people know about republican culture the less power it will have to slow and derail this important work. The more truth republicans know about republican culture, the fewer republicans there will be.