We know that fascists like too mythologize the past, And origins of different ethnicities, so when I started hearing about French fascism in the 20's-40's I wondered, what part of French history would they mythologize?, And what would they consider be the National origin of France? Any particular disagreements between French fascist/Far-right politicans, on the Origin of France and it's people?
Tldr: I want to know which French fascist/Far-right groups identified France's national origin as either the Celts, the Franks or the Romans
This is something I can kind of answer. The person and organization I will focus on are Charles Maurras and the Action Francaise. Now, few historians consider Maurras a fascist, but he was undoubtedly a far-right royalist and integral nationalist. One of the first fascist parties, Le Faisceau, was founded by Georges Valois was involved in the Action Francaise for several years. Maurras definitely engaged in the mythologization of history. He viewed the French as a Latin people. The Roman Empire brought the civilizing mission to Gaul. Thus the Celts were transformed into Gallo-Romans. His Germanophobia was so severe that he refused to believe that the Germanic invasions of Gaul during the early medieval period had any influence on the developing French kingdom. Maurras did not have much to say about the origins of the French. He was more concerned with the medieval period with its magnificent kings, especially Louis XIV.
Sources:
Eugen Weber, Action Française: Royalism and Reaction in Twentieth-Century France, (Stanford: Stanford University Press, 1962)
Stephen Wilson, "Fustel De Coulanges and the Action Française," Journal of the History of Ideas 34, no. 1 (1973): 123-34.