using LukeHagar.PlexAPI.SDK;

var sdk = new PlexAPI();

var res = await sdk.Server.GetServerIdentityAsync();

// handle response

{
  "MediaContainer": {
    "size": 0,
    "claimed": true,
    "machineIdentifier": "96f2fe7a78c9dc1f16a16bedbe90f98149be16b4",
    "version": "1.31.3.6868-28fc46b27"
  }
}