Most of this discussion is found in The Dawn of Everything Chapter 2, Wicked Liberty (pp. 27-77). The main intellectual figure that Graeber and Wengrow refer to is the Wendat statesman and philosopher Kandiaronk.

The first move they make is reaffirm Kondiaronk's historicity, i.e. show that Kandiaronk was a real person who, at the time, was engaged in a Bismarck-esque 'complex geopolitical game, trying to play the English, French and Five Nations of the Haudenosaunee off against each other [...] with the long-term goal of creating a comprehensive indigenous alliance to hold off the settler advance' (Graeber & Wengrow 2021: 49).

Graeber and Wengrow assert Kandiaronk's historicity by reference to multiple French sources from the time, but especially an extremely popular book by the Frenchman Louis-Armand de Lom d'Arce, Baron de la Hontan (known in short as Lahontan) called Supplément aux Voyages du Baron de Lahontan, ou l'on trouve des dialogues curieux entre l'auteur et un sauvage de bon sens qui a voyáge (1990 [1703]). Lahontan was a French aristocrat stationed in Canada, who had numerous interactions with Kandiaronk (which he documents in the above book, albeit giving Kandiaronk the name of 'Adario'), in which Kandiaronk extensively critiqued French social arrangements of the time. Furthermore, they also refer to indigenous oral literature about Kandiaronk, as documented in John Steckley's (1981) book Untold Tales: Four Seventeenth-Century Hurons.

To give you a flavour of some of Kandiaronk's critiques, here's one sample (Graeber & Wengrow 2021: 54). Note that Kandiaronk's allusions to Wendat society lacking law should be read in the context of the rhetorical, embellished nature of these debates -- the Wendat did have a legal code:

Lahontan: This is why the wicked need to be punished, and the good need to be rewarded. Otherwise, murder, robbery and defamation would spread everywhere, and, in a word, we would become the most miserable people upon the face of the earth.

Kandiaronk: For my own part, I find it hard to see how you could be much more miserable than you already are. What kind of human, what species of creature, must Europeans be, that they have to be forced to do good, and only refrain from evil because of fear of punishment?

You have observed that we [the Wendat] lack judges. What is the reason for that? Well, we never bring lawsuits against one another. And why do we never bring lawsuits? Well, because we made a decision neither to accept or make use of money. And why do we refuse to allow money into our communities? The reason is this: we are determined not to have laws - because, since the world was a world, our ancestors have been able to live contentedly without them.

Secondly, Graeber and Wengrow refer to extensive accounts of indigenous critiques of French society as documented by early Jesuit missionaries in the New World, especially the multi-authored, 73-volume The Jesuit Relations and Allied Documents: Travels and Explorations of the Jesuit Missionaries in New France 1610-1791 (Gold Thwaites (ed.) 1896-1901) and Brother Gabriel Sagard's Le Grand Voyage du Pays des Hurons (1938 [1632]).

These were mostly in the form of rejoinders by everyday indigenous people to the missionaries' attempts to try and convert them to Christianity. This is based on Graeber and Wengrow's intentionally broad definition of the term 'intellectual' as 'anyone in the habit of arguing about abstract ideas' (Graeber & Wengrow 2021: 35), although this in itself alludes to the Jesuits' observations that the New World people 'nearly all show more intelligence in their businesses, speeches, courtesies, intercourse, tricks, and subtleties, than do the shrewdest citizens and merchants in France' (Jesuit Relations 15:155, in Graeber & Wengrow 2021: 45-6).

As I mentioned above, if you do get the book, you'll find all of these arguments in its Chapter 2. Even so, here are some of the primary/secondary sources they cite (excluding the ones I've already cited above), which might be especially interesting in regard to your question:

Ellingson, Ter. 2001. The Myth of the Noble Savage. Berkeley: University of California Press.

Grinde, Donald A. 1977. The Iroquois and the Founding of the American Nation. San Francisco: Indian Historian Press.

Harvey, David Allen. 2012. The French Enlightenment and its Others: The Mandarin, the Savage, and the Invention of the Human Sciences. London: Palgrave.

Mann, Barbara Alice. 1997. 'The lynx in time: Haudenosaunee women's traditions and history'. American Indian Quarterly 21 (3): 423-50.

Mann, Barbara Alice. 2000. Iroquoian Women: The Gantowisas. New York: Peter Lang.