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.
I sunk hours upon hours into this mod. Highly recommend getting this mod!