December 2022 (Western) survey of religious demographics in Iran: Shia Islam (38%), Deist (26%), None (9%), Atheist (7%), Sunni Islam (5%), Zoroastrian (5%), Sufi (3%), Agnostic (3%).
Nobody wants to admit they are Christian in Iran. It’s a death sentence to be Jewish or Christian in Iran.
However, in 2020, a million Iranians were secretly polled and admitted to being Christians. It has undoubtedly gone up from there in four years.
I can say for certain that almost all mosques are empty on a daily basis. They may state that the are Muslim, but their actions speak otherwise.
That million is what people are admitting to in secret. Remove the regime and threat of death and it’s almost certain to be much greater than that.
That sounds like a survey of Iranian-Amerhcans, not of Iranians in Iran. It would be interesting to compare various sources and estimates.