We missed updating folks back in November when A Total War Saga: TROY got a major update that included the ability to play the game's campaign in two player co-op on top of co-op skirmishes. That feature, when launched, was considered beta and not completely finished. As to be expected folks encountered numerous issues.
Creative Assembly, the game's developer, have released a hotfix for the game that addresses a handful of issues, the biggest of which is the desync players were experiencing at the end of their turns.
1. Fixed an issue that resulted in the game appearing as “modded” permanently
2. Fixed an issue with unit compositions becoming stretched and entities stacking on top of each other (spaghetti lines)
3. Fixed a problem with mod loading that prevented mods, that override retail files completely, from loading
4. Fixed a multiplayer desync that occurs during the end-turn sequence
5. Localization updates
The mode still isn't out of beta, but according to the Total War forums the team is continuing to take feedback and work on improvements. Currently A Total War Saga: Troy is an Epic Store exclusive with a release on Steam coming in 2021. Here's the full list of co-op features.
MULTIPLAYER BATTLES
- Allows any player to host a new multiplayer battle lobby or join an existing one and customize the experience
- Customization options include: battle type, battle map, battle difficulty, time limit, funds, time of day, weather, and unit size (new to Total War!)
- Extra toggleable features include unit caps, battle realism, large armies, and all mythical unit rosters
- Allows players of the same alliance to communicate via drawing on the in-game map using the Map Markers feature
- The use of community created maps via mods is also fully supported
MULTIPLAYER CAMPAIGN
- Allows any player to host a new multiplayer campaign lobby, join an existing one, or resume from a save game
- Customization options include: game mode selection between head-to-head and co-op, turn time, battle limit, default battle resolution (allowing players to choose what happens to a battle if players fail to agree in time – autoresolve by default, fight by default, etc.), unit sizes, and campaign difficulty