In my view, the only solution is the complete dissolution of all but one armed groups, full accountability through trials for every leader involved, and a new constitution that puts civilians in charge and rejects colonial identity categories entirely.
FIFY.
The civilians themselves should become the only legitimate force in the country. What I am proposing is the complete removal of the current leadership, every faction and every general, followed by a new government built by the people and enforced by the people. I am talking about the Sudanese population that wants the military elites out so they can finally live in peace without proxy warriors tearing the country apart. This will require some level of outside support, and it is unfortunate that the United States, like most superpowers, is too self-interested for an idea like this to be taken seriously.
So who's the one armed group that enforces the new government?
1. The people themselves,. i.e., give a gun to everyone? There's a famine going on, so nearly everyone who doesn't use it to become a robber will sell his gun to buy food.
2. A new security force made up of Sudanese loyal to democracy, that disarms the RSF, the traditional army, and the various rebel factions? History suggests it will just stage yet another coup. Sudan has an Arab majority, and Arab military culture isn't kind to democracy -- troops tend to be loyal to their units, their clans, their officers, anybody but their country; and Sudan is coup-prone even by Middle-Eastern standards.
3. The Americans? The U.S. isn't going to invade to restore democracy -- the majority of the Sudanese favor Sharia, Arab supremacy, and contempt for the rights of minority groups. The U.S. won't be up for enforcing that. If the Americans are brought in to shore up a new civilian government we'll insist on equal rights and secular government, and then the majority will be against us and new armed opposition groups will spring up.
4. An Arab foreign power? The African Union? Either of those will be perceived, probably correctly, as just muscle for one of the local factions.
5. Who else is there? China? That might be the least bad option.