Disclaimer: I can’t claim that the individuals below are 100% lifetime naturals. There’s no way of knowing that.
Fortress a.k.a. Pavel Rudometkin has a YouTube channel dedicated to bodyweight training. His physique is achievable naturally. Nattyornot.com has already done a “review” of Fortress. You can read it here.
Lui Marco owns one of the oldest YouTube channels dedicated to bodybuilding. He has thousands of videos dedicated to muscle construction. In theory, Lui Marco’s physique can become a reality naturally. You can read nattyornot.com’s post on him here.
Lyle McDonald is known for his “fuck you” behavior, but since he has The Info, people keep going to him. I think he is natural.
Lifting for life is a channel owned by the fitness nerd Ian McCarthy who also has a physique that can be achieved naturally.
The OfficialBarstarzz YouTube channel is dedicated to calisthenics. The videos include many athletes and not all of them are natural. However, most people who are into bodyweight training do not take steroids because the sport does not require it.