The most straightforward way to look at it is that, technically, no, Eren is not a Titan anymore in the most recent chapters. The Founder Ymir is finally free, the Titan powers are gone from the world, and all the existing Titans revert to human form. That includes Eren. His colossal form crumbles away and we see his head, just a human head, separated from his body. So in the literal, physical sense, the answer is a clear no.
But I don't think that's the whole story, and it's why the question keeps coming up. The entire final battle happens because he is the Founding Titan, commanding the Rumbling. His consciousness is literally spread across the Titan skeleton spanning the planet. Even after his physical death, his essence or his impact isn't just gone. He's not a Titan, but he died as one, and his last moments were spent inside that form, connected to paths and all the Eldians. It feels weird to say he stopped being a Titan the second the power vanished, because that identity defined him for so long.
Maybe the more interesting angle is whether he ever stopped seeing himself as one, even after he lost the power. His plan required him to become the ultimate monster, the devil of the world. In a symbolic sense, he became something even bigger than a Titan, a concept of terror and, in his twisted logic, salvation. So while the latest chapters show the power itself eradicated, the shadow of Eren the Titan, and the memory of what he did while wearing that form, is permanent. That's the part that sticks with you after closing the manga.