I would have zero problem with this. As long as he's a well rounded character, I don't think including a trans backstory that he's private about ICly is going to come off as looking for oppression points.
Actually, I prefer something like that not to be an ongoing focus of the character. It's OK if it is a big focus of the character, if it makes sense for their setting or backstory, but I kind of like seeing stories about, for instance, trans people that are about them being people, not about them being trans.
(I will say that I don't have concerns about the 'futuristic medicine' example, so long as the setting is something that matters in plenty of different aspects of the character's backstory. The only thing I'd be concerned about is if the "far future sci-fi" only comes up as a reason for not having to deal with ongoing aspects of transitioning.)
Re: Trans Characters
Actually, I prefer something like that not to be an ongoing focus of the character. It's OK if it is a big focus of the character, if it makes sense for their setting or backstory, but I kind of like seeing stories about, for instance, trans people that are about them being people, not about them being trans.
(I will say that I don't have concerns about the 'futuristic medicine' example, so long as the setting is something that matters in plenty of different aspects of the character's backstory. The only thing I'd be concerned about is if the "far future sci-fi" only comes up as a reason for not having to deal with ongoing aspects of transitioning.)