You’re right that Fairphone’s supply chain is not fully sustainable. In fact, I remember reading an interview with the founder where he admitted that poor sustainability and labour practices are so entrenched in the industry that it was impossible to actually make a “fair” Fairphone. (Incidentally, this is why the company uses the word “fair*[er]*” to describe the phones.)
Yeah, I would definitely agree that a used phone is a much more environmentally-friendly choice than a brand-new one. The amount of customers who are going to ditch their 1 or 2 year old phone for this “sustainable” phone will unfortunately not be zero…