Feel like I have a really good experience to weigh in with here. I had pubertal gyno on both sides since as far back as when I was like 14-15 going through puberty. Only really noticable as puffy nipples when I was warm, my chest fat distribution helped to hide it really well, and if my nipples...
I go at 10pm or 5am. The only other people in my gym are chill old people that do cardio and circuits on the machines. A few of them say hi and good morning to me or we just nod and acknowledge each other. At night it's usually fat people doing cardio or one or two guys just minding their own...