The status of "nothing is" is very sensitive what the context of "is" is.
The radical skeptics like Pyrrho would withhold assent to even the most trivial everyday things, it is always "it seems so" to them, never "it is so", so they would not utter "nothing is". On the other hand, this can be seen as even more radical than nihilism, denying the possibility of asserting existence of anything in the first place, and of denying it as well. The second most influential figure in Buddhism, Nagarjuna, the sage of emptiness, is perhaps most often accused of metaphysical nihilism. His writings are full of subtle dialectic arguments for how everything that the traditional metaphysics posits to be — things, elements, souls, world, nirvana, etc. — is not. But his nihilistic tetralemma is more along the lines of Pyrrho:
"We do not assert “empty.” We do not assert “nonempty.” We neither assert both nor neither. They are asserted only for the purpose of designation."
And as Garfield explains in Madhyamaka is Not Nihilism, modern scholars interpret Nagarjuna as contrasting two perspectives, conventional and ultimate:
"The ultimate perspective is that of a fully awakened being — a buddha — from which all things appear as empty of any intrinsic identity or essence, as
interdependent, and independent of their presentation by conceptual thought, or as described by social or linguistic conventions. While... we can’t say anything at all from the ultimate perspective in virtue of its transcendence of the discursive, there is quite a bit that we can say from the conventional perspective."
This is in tune with a wide current in modern philosophy called anti-realism (the term was coined by Dummett, but the viewpoint much predates him), which can also be interpreted as saying that everything the traditional metaphysics talks about, substances, attributes, minds, etc., is not. The difference is that there is no "ultimate perspective" either. What they reject is not so much the "isness" itself as the classical idea that there is some "objective", perspective-independent, content that can be placed in front of "is". Kant reduced it to the transcendent "thing-in-itself" of which nothing can be said or thought. But as Wittgenstein put it in Philosophical Investigations "a nothing will serve just as well as a something about which nothing can be said". But rather than answering "nothing" to "what is?" anti-realists are more likely to say that the question is a pseudo-question loaded with metaphysical misconceptions.
There is a very close modern position of (quasi)realism, which redefines ontology in non-metaphysical terms, and thus escapes the necessity of outright anti-realism (Quine and Putnam are examples). Turner gives an interesting analysis of Ontological Nihilism from this perspective:
"Ontological Nihilism is the radical-sounding thesis that there is nothing at all. Almost every one believes that it is false. But this does not make it philosophically uninteresting: we can come to better understand a proposition by studying its opposite... Ontological Nihilism faces a dilemma: if it is to be viable, avoiding the ills of Quiet Nihilism, it must embrace a particularly holistic picture of reality with an attendant bloated ideology and brute entailments."