There is this historiography of the Quiet Revolution that I hear a lot, where we are supposed to talk about Quebeckers rising up in the 1960s and 70s, becoming "maîtres chez nous", and doing things like, say, forming the Hydro Quebec monopoly, or throwing off the Catholic Church in favour of a modern welfare state (and so on) as a way to assert ourselves.
But it seems to me that in its own way, the Duplessis period was also marked by a great deal of nationalism: for example, by its rejection of federal intervention in domains which were supposed to be provincial affairs. So what gives? Are we just talking about a changing depiction of what "nationalism" is supposed to mean?
You make it sound like there is an opposition between the Quiet Revolution and Duplessis when there isn't really one. Both are important moment in the rise of Québec nationalism and just display a different type of nationalism and is a perfect example of the changing nature of nationalism in a given territory.
Nationalism under Duplessis was about French-Canadians of a Catholic heritage. No talk of separation neither; it is about preserving the place of French-Canadians in North America or Canada and have them be witness to the survivance of catholicism in a sea of protestant believers. Economic nationalism and civic nationalism was different at this time than during the Quiet Revolution, with the economy mostly controlled by English speakers and the civic aspects of life under control of the Catholic Church.
In the end, both the English and the Catholic Church controlled central parts of Québec society. Being French-Canadian was an identity strongly based on its Catholic roots, rural status and working class status. Being a Québécois (although the term would be anachronistic back then) meant being Catholic and a member of the working class. Duplessis himself saw his role as one where he was supposed to protect the Québécois against the possible over reaching of outside powers trying to over-exploit the province. He would end up opposing the conscription or the involvement of Canada in the World War and his policy was often based on keeping the Catholic Church in place and ensuring that foreign companies would give work to French-Canadians.
Nationalism with the quiet revolution took a different turn: it meant redefining Québec identity to some level, first by dealing with the Catholic Church. Most Québécois did not have issues with the Clergy and recognized the importance of their work in Québec society but sought to limit its power and influence. Québec nonetheless ended up violently cutting its ties to religion by North American standards and hospitals and schools eventually told the Clergy that their hospitals and schools would move toward secularism and be taken under the wing of the government. The move toward the welfare state was essentially a way to give Québecois people their institutions instead of depending on what is technically an institution managed from Italy.
In regard to the economy, it was decided that English Canada and the United States would not be in charge of important sectors of the economy. I have written a relatively short answer regarding Hydro-Québec specifically (See: https://www.reddit.com/r/AskHistorians/comments/5c1wkj/how_did_foreign_markets_react_to_the/?st=iwqvtebb&sh=bfdc10ea) but overall, vital sectors of the economy such as electricty was seen as being under control of foreigners who were usually not seen as having the interests of Québécois people at heart. Electricity has a special place as a sector when it comes to how nationalists conceptualise their emancipation but basically, in the case of Québec, it became a symbol of taking control of their own economy in a Québec that did not have a strong economic hold on its institutions. A good example is how electricity companies did not want to hire French-speakers and Hydro-Québec became vital for French-speaking engineers to find work and eventually make the profession one dominated by French-speakers in Québec.
So how did nationalism change from Duplessis to the Révolution tranquille? What it means to be a Québécois changed and as it affirmed itself as a nation, it sought to gain control of its institutions from outsiders (the Church and the English). Rejection of religion and language issues would eventually become central to what it means to be a Québécois (and might also contribute to an explaination of the differences in how Québéc perceives religion compared to the rest of Canada but that is a different story; but also the focus of some of my research).
It's basically a different kind of nationalism. Your analysis is pretty much spot-on. As in many things in history, there's not a clear cut answer and many intro courses give only one narrative frame that leave out the whole complex process behind the scenes.
Duplessis was heir to the clerical nationalism tradition where the french-canadian church and the political elite agreed upon given roles to manage the province of Quebec. People self-identified with a french-canadian identity that transcended the frontiers of the province.
However, the quiet revolution is a shift from the past in the sense of the full self-recognition of Quebec as a nation. In other words, the quiet revolution is a shift from french-canadian identity to a new Québécois identity. It crystallised many pre-existing facets of the society into a new conception. Under Duplessis, society was seen as under-developped and not yet fully modern, still under the heels of anglophone interests & economic domination, at the hands of church elites and small time politicians.
Duplessis evoked many of these issues himself, but he is seen as a indicator of the 'great darkness' before the quiet revolution. Evidently, the expression 'the great darkness' is troublesome and we must put it in perspective, as Duplessis had many nationalist and modern aspects, and these issues were not about a single man. However, Lesage election was a break from this era and gave the signal for a renewal. Maîtres chez nous is the most famous slogan maybe, and underlines the fundamental problem with Duplessis.
It's made manifest by the rejection of church involvement in moral conduit, in state affairs and in services. It's also the construction of the Quebec technocratic state along with social-democratic services. The great works of nationalisation of hydro power, construction of colleges (CÉGEPS) and Universities funding, etc.
Also, please note that nationalism and nation has a much broader meaning in english than it does in french. It sometimes boggles the debate on Québec nationalism.
I suggest reading Fernand Dumont, Marcel Trudel, Stéphane Kelly on this question.
Yes, Duplessis is a real nationalist (within the actual definition of nationalism)