In mainland China, probably not tolerated outside of like the context of museums. Idk about the laws, but at the minimum, cops will probably visit you and “have a chat”

Gotcha, that's closer to what I had thought.

I’m Chinese-Amercian, I was born in Guangzhou, but I’m no longer PRC National anymore so I don’t give a shit what mainland nationalists think. I think ROC flag is fine overseas…

Oh certainly! It was not rare when I visited Flushing.