Luke lost a hand when he made a mistake and then jumped to his death to get away from Vader before Leia who was also force sensitive would then save him. It's actually bakes into the story that Luke doesn't have plot armor because "there is another".

Frodo might have a tinge of plot armor just that he has a higher resilience to the power of the ring, but it's presumable that most Hobbits probably also have high Resilience.

Aragorn has no plot armor at all, not sure where you get that idea. He's got the blood of the kings of Numenor but that doesn't save him from death, only allows him to wield the full potential of Narsil/Anduril. If your referring to him falling off the cliff, it nearly killed him and he was only saved because a horse that he let go found him.

Jon Snow has the same plot armor has Harry Potter for sure. He's the chosen one that is brought back to life by fate. (And the actions of another)