I understand it's frustrating. You can still control yourself (boundaries) even when you don't have control of your situation. Consider that even people in prison can benefit from healthy boundaries.

For example, you can choose to engage or not engage in arguments , complaints, or other conversations that aren't productive. You choose whether or not to look at other people's phones. You can choose where to put your emotional energy. Worrying about whether or not people are talking behind your back is a choice that only you can control.

For example, if a person on the street comes up to you and starts ranting, you probably wouldn't take it personally and engage in discussion. You have the same choice in your family.

Unrelated- You didn't mention why it is you can't leave. Personally, I would rather sleep on the floor of a rented room or van than feel helpless in someone else's home. I know this is a very American point of view that may not apply to you.