Reproduction steps:
1. Create a new project
2. Open Multiplayer Center window (Windows > Multiplayer > Multiplayer Center)
3. Select any Genre of your Game and Number of Players per Session
4. Press “Install Packages” button and observe the console
Actual result: “The type Unity.Multiplayer.Center.Editor Unity.Multiplayer.Center.Window.RecommendationTabView is being serialized by [SerializeReference], but is missing the [Serializable] attribute. To suppress this warning add [Serializable] or use [MakeSerializable].” warning is thrown
Expected result: No errors or warnings are thrown
Reproducible with: 6000.3.0a5 (36d7e9fd6645), 6000.3.0b4, 6000.4.0a1
Not reproducible with: 6000.0.59f1, 6000.2.7f1, 6000.3.0a4
Couldn’t reproduce with: 2021.3.57f1, 2022.3.67f1 (No Multiplayer Center window)
Reproduced on: macOS Sequoia 15.4 (M4)
Not reproduced on: Windows 11