What is ethno-nationalism?

Ethno-nationalism is defined as "advocacy of or support for the political interests of a particular ethnic group, especially its national independence or self-determination." Ethno-nationalism is also sometimes referred to as "identitarianism," or identitarianisme in France where these ideas originated. Ethno-nationalists seek a singular definition for national culture. It often subscribes to the notion that the West should be characterized as Christian and white.
In Europe, ethno-nationalism has surfaced as the advocacy of "blood and soil," or the understanding that people who are ethnically French, for example, have an obligation to preserve their culture and ethnic identity in response to immigration and non-European influences, such as Islam. What ethno-nationalists forget is that countries in Europe have historically been influenced by "outsiders." French people, for example, are not "purely" French. In fact, the concept of French purity may not make much sense at all, given that French culture was historically influenced by two groups: the Gauls, a Celtic people, and the Francs. Since then, there have been plenty of other cultural influences and ethnic admixtures from other European countries and, later, from former French colonies, such as Algeria. The aversion to increasing ethnic and racial influences that are non-European suggests that the concern is not over a fading national identity but over a fading white identity—or, a declined association of French or German or British identities as decidedly "white."
In France, proponents of ethno-nationalism, or identitarianism (defining national identity according to race or ethnicity), include Renaud Camus, Guillaume Faye, and the novelist Jean Raspail. Their ideas have influenced figures such as Marine Le Pen, the former French presidential candidate from the National Front Party, and, in the United States, Steve Bannon.
https://www.lexico.com/en/definition/ethnonationalism

https://www.newyorker.com/magazine/2017/12/04/the-french-origins-of-you-will-not-replace-us

https://www.theamericanconservative.com/articles/what-is-ethno-nationalism/