In what way did organizations like the True Reformers and St. Luke’s Society help Africans Americans in terms of mutual aid?
When we talk about mutual aid, we are usually talking about organizations that are set up to provide assistance to one another. Mutual aid societies typically do things like collecting money from all of their members and using that money to help members when they are in need. That is the sort of mutual aid that was provided by the kinds of groups that you are asking about in this question.
For example, the Independent Order of St. Luke provided insurance to African Americans. White insurance companies would not sell insurance to African Americans. Therefore, the IOSL pooled money from its members and used that to pay out benefits to those who were in need.
The True Reformers did similar things. They, too, had an insurance set up. They also created a sort of moral educational system for children. Children of members would attend these schools that were set up to teach things like thrift and temperance. The True Reformers branched out beyond things like this to set up, for example, a bank.
Both of these groups, and others like them, provided benefits such as insurance and payment for burial to African Americans who would typically not be able to buy them on their own.