perhaps you may try here:
https://m4uhd.tv/watch-movie-flavia-the-heretic-1974-228333.html. i've had the complete movie sometime but it was lost with the rest of my collection on the corrupted hard drive, alas.
this's typical italian old school exploitation of 70th (strictly say, the late nunsploitation classics) - partly pretty brutal, almost without limits on sex & cruelty, partly a few naive, basically quite moralistic despite massive fucking and violence - a proper catholic art
the plot is based on the true story of the 15 century when the ottomans invaded the apulia province in the south of italy. flavia is a dare, disobedient and free-spirited girl who was forcibly tonsured as a nun by her abusive father, the local big boss. the otranto convent where she's "imprisoned" in fact, is known for its extremely strict discipline however actually it's the true sink of iniquity, the most heinous depravity as well as various barbarity and violence, sexual and not only where holy fathers, priests, and monks (i don't remember what they do there), with a vengeance revel in bullying and torments of nuns and laic women.
flavia rebels against this male power of the devotee torturers, tries to fight it, then escapes from the convent but unsuccessfully and gets severe punishment afterward. surely she's destined to perish here one way or another. no wonder that when the muslim (ottoman?) army invades the rebellious girl throws off her nun's cap, renounces christianity (so, the heroine is apostate or renegade in fact, not heretic), joins the invaders, and together with them starts to take revenge on her former co-religionists, fellow citizens, father etc: actually she dreams of destroying this native but hostile to her world and now should "launch rivers of blood" (according to the movie's slogan).
besides flavia falls into mad dark passion (or lust?) to the muslim general minded to take her into his harem but sees soon that he's also just a brutal male, and eventually refuses to obey him too, so when invaders sail from apulia with plundered treasures and lots of enslaved christians, their leader leaves flavia and abandons her alone on the shore: beaten out, devastated, exhausted, the doomed renegade girl lays stretched out naked on the cold beach boulders, along which she will go barefoot towards the cruel torture and terrible death...
In final, her execution - skinning alive - is shown at the highest degree sparingly unlike all previous episodes of the atrocities, blasphemy and lechery, without those expressive graphic bloody details (splendid, really!) that we've seen recently in the french "martyrs". despite such minimalism, however, this is one of the most tremendous, suggestive, rich eros & tanatos, and simply arousing torture scenes in the world cinema, since the heroine's painful agony was skillfully identified here with her sadomasochistic sexual intercourse. flavia is fucking by herself literally, suffering and pleasuring at the same time while anticipating and enduring her agonizing execution: a long prelude to the sounds of drumming: the procession of priests and executioners with the victim in white sanbenito at the head is slowly climbing the hill of death along a kind of apostate's "via dolorosa" - shackled bare dirty feet on sharp road gravel is replaced the desperate look of defiant eyes - tormented face is demonstrating the signs of a twilight altered state of consciousness, a sort of subspace - a keen looking forward to forthcoming pain and pleasure is mixed with a vague memory of past pleasures and pains - a flap of skin heavily peeled off from a leg is stripping the trembling flayed flesh - the painful groan of anguish and voluptuousness turning into the shrill cry filled of pain-and-passion is melting into the boundless sky...
in my next post, i'll re-post the excellent web comment from an unknown to me person. guess his (or rather her) text describes the movie much more complete and deep than my note.