psstein has claimed that Farmer was wrong, back in 1870's there were Catholics quite independently of Prussian pressure who were for Marcan priority.

Now, I checked, Miracle Tradition, Rhetoric, and the Synoptic Problem, By Duncan Graham Reid actually has a kind of overview of the history.

I checked name after name in the fairly short chapters on the early history of the controversy.

And - thanks to wikipedia - all I find is Protestants:

1.2.1 Origins of the Modern Debate in the Eighteenth and Nineteenth Centuries
1.2.2 Early Twentieth Century Developments

Hermann Samuel Reimarus - Protestant
Johann Jakob Griesbach - P
Ferdinand Christian Baur - P
Christian Gottlob Wilke - P
Gotthold Ephraim Lessing - P
Johann Gottfried Eichhorn - P
Johann Benjamin Koppe - P
Herbert Marsh - P
Karl Lachmann - P
Johann Gottfried von Herder - P
Karl August Credner - P
Heinrich Ewald - P
Heinrich Julius Holtzmann - P
Paul Wernle - P
William Sanday (theologian) - P*
Willoughby Allen - P
J. Vernon Bartlet - P**
Burnett Hillman Streeter - P
John C. Hawkins - ? - P***
Philipp Vielhauer - P
Willi Marxsen - P

* Since: He was Dean Ireland's Professor of Exegesis of Holy Scripture at Oxford between 1883 and 1895
and since: The position of Dean Ireland's Professor of the Exegesis of Holy Scripture was established at the University of Oxford in 1847. This professorship in the critical interpretation or explanation of biblical texts, a field known as exegesis, was instituted by John Ireland, who was Dean of Westminster from 1816 until his death in 1842.
Dean of Westminster is not a RC position

** Since his work "The apostolic age; its life, doctrine, worship and polity" has no Imprimatur or Imprimi potest, an impossibility for a Catholic work back then. If published, that is.

*** Since in a seminar under the leadership of Sanday.