I was checking the official documentation from Microsoft and it states that the FeatureGate attribute can be used to control whether a whole controller class or a specific action is enabled. I've installed the Microsoft.Azure.AppConfiguration.AspNetCore 4.2.1 and even 4.3.0-preview but I can't find it:
using Microsoft.FeatureManagement.Mvc;//doesn't recognize .Mvc it recognizes up to Microsoft.FeatureManagement
[FeatureGate(MyFeatureFlags.FeatureA)]//doesn't recognize FeatureGate either