Divide and Conquer is the biggest Third Age: Total War submod. The latest release was V5 on July 23rd, 2023. DaC V5- A Kingdom Reuinted features all previous content as well as new features such as the Reunited Kingdom, faction overhauls for Dunland, Enedwaith and the Vale of the Anduin, and overhauled UIs.
The best submod for Third Age Ive ever seen, it really brings life to Middle Earth. The turn time is quick, the AI has well balanced armies and the number of nations makes it harder for one faction to become a giant.