Thinking of images is also different than thinking of words (since all of us speak the language).
I’m not saying it’s impossible, but that I suspect its more likely a lack of introspection - I’d need to be persuaded empirically somehow and don’t know how to test it.
No more of speak the language than see with our eyes. Personally while I do have some kind of inner voice, my thoughts tend much more heavily to the visual. And memories too. If I need to recall a phone number or spelling then I'll imagine it written.
Like you, I had a hard time believing people were different in this. The whole idea of an internal narrator seemed absurd to me. Why would anybody need a narrator for themselves? They're right there! But enough people claim that this is their real life that I'm willing to believe it, however tedious and exhausting that sounds to me.
Without language and semantic meaning tied to ideas, what does 'thinking' mean at all?
My point is more that there are always thoughts (typically in the form of words, but sometimes images) flowing through your mind all of the time. Meditation and 'mindfulness' is focused on recognizing them as they happen and getting control of that kind of thing (at least enough to reduce thought loops, rumination, unwanted emotional response, etc.).
I get that you have a hard time understanding thinking without words because that's your main experience. But please understand that it's different for other people.
And not just people. Animals can be very thoughtful. Watch documentaries, for example, of animal cognition and problem-solving. From crows to chimps, an awful lot of thinking happens, just not in words.