Ownership refers to card ownership.
Your quanta is not a card, thus it is not affected/protected.
Nightmare gives you cards that are not yours, thus it should be prevented.
RT does not change the ownership - it was your card, it remains your card.
PU/Fractal on your own card does not change the ownership - original was yours, new one(s) is (are) yours.
PU/Fractal on opponent's creatures is more problematic. On one hand you get a copy, not the original, so it should be fine. On the other hand you do gain ownership of a foreign card, so not fine.
I'd say it shall block PU/Fractal altogether. Everyone should be able to decide which one (Pu/Fractal or Jarl) they want to use in their deck.
Will update card text to "all card ownership changing effects" tomorrow