I have an inner voice but I don’t use it when I’m reading, which is maybe why I am a very fast reader.
I tend to use it when pondering on things. That said I just noticed that when composing and cross-checking this text for posting, I also used it.
Curiously, nowadays my inner voice is not just in my own mothertongue but can be in just about any of the languages I know enough for basic conversation. It’s probably related to, because my foreign language skills are so advanced (I can speak about 7 languages) that I’ve long stopped translating to my native tongue in my mind and concepts just translate directly from those foreign languages. Also, I’ve lived in a couple of countries and as I would eventually end up mainly speaking the local language, my inner voice would also, eventually, end up also using that language.