Let’s Encrypt will provide service to non-government .ir domains by default. If you are not representing a government agency or entity you should be fine.
We cannot provide service to domains owner or controlled by the Iranian government, or any other person or entity on the U.S. Treasury Department’s Specially Designated Nationals list:
https://www.treasury.gov/resource-center/sanctions/SDN-List/Pages/default.aspx
If it comes to our attention that Let’s Encrypt is being used by an Iranian government agency or entity, and if we can confirm the report, we will be forced to stop service for the domain.