Use turbo frame like old iframe?

Not sure is it possible and recommended but I’d like to make kinda widget which pulls html but also css from site B and displays it in turbo frame on site A.
I’v managed to do easy html part, but how to solve css part, so apply css file there from site B ? I’m using Ruby on Rails. If I will include some css link in that turbo frame it will be scoped to the given frame ?
Of maybe turbo frame is not the best approach and I should rather use embed tag or object ?