The US State department provided specific authorization empowering telecom companies (incl. Starlink) to operate in Iran and disregard local restrictions. If you can smuggle a dish into the country, you can use it. But the signal wouldn’t be too hard to detect, so it’s risky.
What about a special reduced uplink power mode, with only 128Kb of bandwidth for example? Additionally, you can conceal the dish from terrestrial detectors, by putting it in a forest clearing for example. Those two things combined might make it a lot more difficult for the Iranian government to find a Starlink dish.
