Since the first commandment is "Thou shalt have no other gods before me" you could say that Christianity is explicitly polytheistic. Of course, the phrase "the one true god" is also found in the texts of many different faiths. Implying that "other gods" are all frauds.

"Frauds" but still conceivably as real?

A fraudulent god; there's a concept.

One of the Five Pillars of Islam is the shahada: “there is no god but God [Allah]”.

I think you can find statements to similar effect in both old and new testaments of the Bible, even though early Judaism didn’t deny the existence of other gods.

I've been watching Hercules TLJs and Xena TWP lately. In many ways they explore multiple religions and allow them to coexist without conflict. I think they had Archangel Michael talk about reincarnation, they said hell was worse than Tartus, and mentioned karma. They did make Michael who is just an angel more powerful than Hercules though who is a demigod, and Callisto who was a full god at that point and made her into a demon under Satan, so they seemed to favor Abrahamic religions over the Greek religions, but in general they seemed to merge the religions of the world well.