R. Yekusiel Yehuda Greenvald wrote a book about Toldos Chasidus in Hungary published in 1921. This story evidently is confirmed (embellished) in Chabad sources by R. Hayim Meir Heimlin who wrote about this in Beis Rabbi. Greenvald wrote that R. Boruch, the father of Rashaz opposed the new way of his son and left as far as possible to the place where Chasidus were still unknown, to Hungary. He left to be Melamed in Munkatch and then to Selush where he died. Only before he passed away he revealed his identity. Assaf writes about the mythological symmetry with father and son. R. Moshe also only revealed his identity before his death and was a wondering Jew just like R. Boruch.
Chabad sources I think would have you believe the Alter Rebbe’s father accepted hasidut late in his life. This appears to be false, however. The gravestone that reads “Father of the Ba’al HaTanya” was probably paid for by his surviving son Yehuda Leib or his Schneerson grandchildren, all of who were Chabadniks.