This is a short story that I'm reasonably certain I read online in the last year or so. It was
most likely at a publisher's website (e.g. Tor) or an online magazine (e.g. Lightspeed), part of a recent "year's best" science-fiction collection. It feels like something published post-2000, and I thought it had been written by Robert Silverberg, though none of the titles in his bibliography that look promising have checked out. [edit: It was actually Bruce Sterling, per the answer below.]
The story follows a man (middle-aged or older) who is a kind of teacher in a city that seems to be set several hundred years in the future of our world. There has been substantial climate degradation, and the city, while considered large, is not large by modern standards. Water conservation is an essential part of everyday life. Technology has also been simplified. The overall feel of the way society works is something like ancient Rome.
The man is really more of a private tutor than a teacher in the current sense. He has several students, many of whom seem to come from wealthy and/or influential families. He is well-respected but maintains several "heretical" views that are critical of the government. It is made clear that your average person could not get away with expressing these views openly, but it is tolerated from this individual.
The man studies the past and is particularly interested in the little he has been able to put together about the Information Age. It seems as though electricity is no longer in widespread use but it's still understood how to produce it. Some old devices still function though the knowledge to create more has either been lost, or it is simply not deemed worth the expense to make them. Communications has more or less collapsed; there is nothing like a telephone network or internet. (I don't think even telegraph-type communications are still in use.)
At one point, the teacher gives a lecture and presentation about the wonders of past technology. It seems as though he has a functioning laptop [edit: apparently just some sort of projector that I assumed was connected to a computer] that he can use to demonstrate videos, which are otherwise unknown. People are largely unimpressed with this. What really stands out about this scene is the man's attempt to describe what the reader recognizes as the modern internet: all things informational are described by the term "virtuality," and he tries to explain that these things were imbued with virtuality to allow them to have information from other places and times.
There is a political revolution in the city, led by the family of one of his students (or possibly the student himself). The teacher becomes a political prisoner and eventually has to renounce his heretical views. He is spared execution but is either exiled or chooses to leave the city. He lives for many years in the vaguely-described hinterlands around the city, and I think he eventually returns but never recaptures his former prominence. I believe he dies relatively soon after returning.