Rome Total War Alexander for Mac, is the official expansion pack in Rome: Total War Gold. This game is still available on Kinguin. Rome Total War Remastered has also been released meanwhile for Mac in 2021 (also works for Apple Silicon Macs) with all the good stuff. Nevertheless, if you own the Gold version (or you want to play the Alexander expansion specifically) then this port might come in handy.
Alternatively there is also Parallels Desktop (a very easy to use Virtual Machine with Windows 11 (free trial of 14 days)) where the game will work fine. More info about that up here: https://www.paulthetall.com/parallels-desktop/
Rome: Total War: Alexander is the second expansion for Rome: Total War. It is set in an earlier time period, putting the player in the role of Alexander the Great. It begins with Alexander’s ascension to the Macedonian throne in 336 BC and lasts for 100 turns, each of which, unlike the original game and the first expansion, Barbarian Invasion, do not represent six months (assuming that it follows Alexander’s actual reign of thirteen years, each turn would represent nearly seven weeks). The game is much the same as the original Rome: Total War, but with fewer factions, different units, and a different map. The player’s goal is to conquer 30 provinces, including key cities such as Tyre, Halicarnassus and Babylon, within the 100 turn limit.