Hello,
Iran seems to have started blocking Signal today.
This is suggested through OONI measurements testing signal.org in Iran: https://explorer.ooni.org/search?since=2020-12-27&domain=signal.org&...
While the testing of signal.org in Iran was previously successful, today every measurement collected so far suggests potential blocking.
You can continue to monitor the accessibility of signal.org in Iran through the above link (which openly shares OONI data collected in real-time from Iran).
~ Maria.