Aha! I just took a look at the code for ASceneCapture2D and it looks like it’s declaring MinimalAPI - so it doesn’t look like you can derive from it.
I thought I had another good suggestion for you in that you could replace the NewSceneCaptureComponent2D property with your own component - but you can’t derive from USceneCaptureComponent2D either for the same reason.
So maybe a better question would be… what are you trying to achieve?