TheCenter is included directly with the v241 server update. No need to download “DLC” for the server. We’ve reduced the server size drastically from about 30 GB down to 4 GB so yeah 😉 Just change your server commandline to host ?TheCenter rather than ?TheIsland or whatnot. No need to specify any Mod ID’s.
You shouldn’t have to do anything to get your old savedata to work on the new official map, should you have old savedata from a TheCenter mod server. However, given that foliage has changed and some geometry has changed, all foliage will likely reset and your bases may get overlapped by some geometry in certain places (though geometric changes were minimal).
If they don’t already have the DLC installed, when players attempt to join your server, they will be automatically prompted to install the free TheCenter DLC via the Steam Overlay.That’s pretty much it. The Anonymous ARK Dedi Server App and TheCenter DLC will be updated in tandem going forward, typically along Major version releases of ARK, so it will be much easier to keep the map in-sync if you host long-running servers.