But, I guess, it could be Protestant since there is no definitive doctrinal authority in Protestantism, just different interpretations of the Bible to suit one's honest preferences. (I do not make that last statement flippantly; I am not denigrating the sincerely held views of others based on conscience. I have strong respect for my Protestant brethren.)
But Catholicism has a central authority which has rejected the libertarian perspective, in spite of the idolization of Ayn Rand by Paul Ryan in the U.S. Congress and other Catholics. This recent Commonweal article does a good job of setting forth the facts about the Catholic view of libertarianism--see link. I myself wrote on the mutual incompatibility of Catholic social thought and libertarianism in the article on "Libertarianism" found in Volume 2 of the Catholic Encyclopedia of Social Thought, which is carried by many university libraries throughout the U.S. and even overseas. Go to WorldCat and find the nearest library carrying the volume (link).
But, of course, labels are fuzzy things. You are likely to find individuals with their own highly adapted, mitigated, and modified version of libertarianism who will claim a Christian foundation for their embrace of libertarianism. As in Protestantism, there is no central authority available to define libertarianism. Thus, often, in a discussion, the anti-Christian character of libertarianism is evaded by clever, adhoc metamorphoses. (The question then remains whether it is libertarianism that is now really being discussed and whether that label now serves any practical use in the discussion. I am reminded of Proteus, the mythological figure who was hard to pin down--see image below. Hence, our word "protean" to signify the elusive.)
In contrast, authoritative, clear, and logical Catholic social teaching is easily located--just go to this Vatican link for an authorized summary of the Catholic view on economics and society at large.
(Image of Proteus below is in public domain.)