It looks like in the update to Unity 2018.3 the iOS Trampoline was updated to remove the MediaPlayer framework and to add the MediaToolkit framework instead. However, while this change was made to the iOS Trampoline, the Native Plugin inspector for iOS plugins was not updated to match. So the current set up means that the MediaPlayer framework is not included and there is no way to add it via the Native Plugin inspector for iOS plugins

To reproduce:

1. Download attached project "iosPluginTest.zip" and open in Unity
2. Select Assets/Plugins/iOS/MiOSPluginUtilities.mm.
3. In the Inspector, notice that the MediaPlayer framework is within the "Default frameworks" list and is ticked so should be included in the Build
4. In the Inspector, notice that the MediaToolkit framework is within the "Rarely used frameworks" list and isn't ticked so shouldn't be included in the Build
5. Build for iOS
6. Deploy the Xcode project to iOS Device

Expected results: The Build will succeed and a program will launch on iOS device
Actual results: The Build will fail within Xcode with a linker error because the MediaPlayer framework hasn't been added to the Xcode project

Tested with:
- iPhone 7 Plus, iOS: 12.0 - Reproduced
- iPhone X, iOS: 11.3.1 - Reproduced

Reproduced on Unity 2018.3.0b4, 2018.3.5f1, 2019.1.0b3 and 2019.2.0a4
Not reproduced on Unity 2018.2.20f1 and 2018.3.0b3
Regression on Unity 2018.3.0b4