I would like to share with you the photos from southern Poland where Orthodox religion had used to flourish and coexisted with Catholicism and Judaism for centuries, until it was suppresed by communists after WW2. Today, Orthodox believers are trying to revive their religion and culture.
Orthodox Churches and Lemko people in southern Poland
This is all well and good, but I think you have your history a bit mixed up. Most of these churches were built in the 18th and 19th centuries when the area was under firm affiliation with Rome, i.e., Greek Catholic.
of these villages mostly switched to Orthodoxy in the 1920s and 1930s. (During the 1910s, the time of the missionary efforts of now-Saint Maksym Sandovych of Gorlice, a few villages began to see some returns to Orthodoxy, but this movement did not involve Greek Catholic church property going over to Orthodox ownership.)
In 1947 the native Lemko Rusyns, of whatever religious confession--Greek Catholic, Orthodox, or Protestant (by then there were some)--were deported in the infamous Vistula Operation (Akcja Wisla)
to the "recovered lands" mostly in Lower Silesia / Dolny Slask. Some villages were then resettled by Poles and the existing churches were retrofitted to serve as Roman Catholic, but most actually fell into ruin or were burned or used as warehouses and barns. In the 1960s, Lemkos were permitted to return to the region, and some did, but only to selected villages, not necessarily their own. In those places, Greek Catholic and Orthodox parishes were reestablished. Thus about half the villages in southeastern Poland with a Lemko population support an Orthodox church/parish, half support a Greek Catholic parish. Some of them go to a neighboring village, having been unable to reclaim their original church from the Roman Catholics, who in many villages still outnumber the Lemkos.
But in other words, if one is to sharply differentiate Greek Catholicism (united with Rome) from Orthodoxy, one should be clear and understand that the period of time when these churches were built and used by the native population was the time of Greek Catholicism, not Orthodoxy.
I would add that the Polish government never suppressed Orthodoxy. Perhaps you are thinking of the 1947 deportations, but it was not a legal action against a religious confession, but against an ethno-national group. Nor was the Greek Catholic Church ever explicitly banned as it was in neighboring Ukraine and Czechoslovakia; its operation was restricted (and was administered by the Polish Roman Catholic hierarchy), but with the massive displacement of the Lemko and Ukrainian population, this set back the life of the Greek Catholic Church in Poland for decades.