Use Redux Toolkit's createSlice with useReducer + export a type union of all its actions defined in 'reducers'

exportActionsUnionFromSlice.ts

// https://stackoverflow.com/a/64582352
export type SliceActions<T> = {
  [K in keyof T]: T[K] extends (...args: any[]) => infer A ? A : never;
}[keyof T];

// USAGE - NOTE: This doesn't work with `extraReducers` and the builder syntax
export type MySlice = typeof slice;
export type StateAction = SliceActions<MySlice['actions']>;
export type SliceReducer = Reducer<IState, StateAction>;

export const useSliceReducer = (initialStateFactory: () => IState) => {
  const [state, dispatch] = useReducer<SliceReducer>(
    slice.reducer,
    initialStateFactory(),
  );
  return { state, dispatch };
};

export type SliceDispatch = ReturnType<typeof useSliceReducer>['dispatch'];