@haralampopoulosjc
Replying via this way since the more replies the longer the chain becomes of showing replies, in response to your question: "Do we know if Saint Justin of Celije supported the Free Serbs?"
I don't know. St. Iustin was a very prolific writer, writing dozens of books and probably thousands of letters (many of which are still being discovered and published today), from what I've read of his, I never saw any reference to the Free Serbian Orthodox Church anywhere.
St. Iustin stopped commemorating Pat. German (who persecuted St. Iustin in his life and tried to stop his funeral from happening) so St. Iustin was not a fan of German. He probably did support the FSOC but to say or mention that in any letters would've attracted the ire of the UBDA, undoubtedly leading to an arrest and perhaps worse.
I believe there was another question about non-commemorators in Serbia besides St. Iustin; I've seen references to a few but they were small. I believe some of the Ostrog Fathers became non-commemorators. Some of the Hilandar Fathers wrote harshly about German but they weren't under him to begin with.
My personal estimate is that there was maybe a fifty to a hundred priests who became non-commemorators in the 1960s, with that number probably dropping off in 70s, 80s, 90s etc.