For turn-based games, the requirements for networking can be quite different from other, more fast-paced games. You are only interested in changes to the game state, and don't really need more granularity than that. Let's take chess as an example.

Player character representation

You don't really need a player character so in order to process input you don't really need a CoherenceSync object. You could use a Client Connection Prefab if you want to have an easy way to implement chat.

Client-side simulation

You might want to have a Simulator to process everything if you want cheat protection, but for a game such as this it could also be viable to simply opt for client-side simulation and then have one of the Clients have authority over the game controller. That is the default setting when adding a CoherenceSync Component. Each client can then talk to the game controller using Commands.