Reproduction steps:
1. Open the attached “EnumSerializationBug” project
2. Open the “Assets/Scenes/SampleScene” scene
3. In the Hierarchy window, select the “InspectForBug“ GameObject
4. Observe the “Enum Variable“ field nested inside “Inner Data 1“ in the Inspector window

Expected result: An Enum field is seen
Actual result: An Integer field is seen

Reproducible with: 2022.3.12f1, 2022.3.29f1, 2023.3.0a9, 6000.0.1f1
Not reproducible with: 2021.3.38f1, 2022.3.11f1, 2023.3.0a8

Reproducible on: Windows 11 Pro
Not reproducible on: No other environments tested