Perhaps we have a terminology mismatch, I tend to use abstract class and interface interchangeably. I’m not sure it’s possible to define a class interface in c++ without using inheritance, what kind of interface are you referring to that doesn’t use inheritance?
I agree, my terms aren’t perfect, but as you stated there isn’t really such a thing as an interface in c++, traditionally this is achieved via an abstract base class which is what I meant by using them interchangeably.
I know there are many things you can do in c++ to enforce an interface, but tying this back to the original comment that inheritance is objectively bad, I don’t think there’s any consensus that this is true. Abstract base classes (with no data members) and CRTP are both common use cases of inheritance in modern C++ codebases and are generally considered good design patterns.