Searched litteraly everything i could and archives, there is no mention of a submarine from Iran sunk, all time search, month and 24hrs search, archives, all Iran outlets and OSINT or reports, there are only reports of damage on a prototype, a very very long time ago, but no sinking
If this was known by western intel and medias, it would be all over internet to mock Iran and the victims, we know very well their reporting on Iran military and the demonization, obsession with Iran military, waiting for anything to mock it. I remember when Iran seized the Stena Impero, there was "The Sun" (literally a big media) that did a video showing IRGC on the ropes that touched another soldier below him. The "kung fu" video and recent misinfo about the quantum processor, 90% of shahed intercepted, photoshop drones and CGI missiles
We would have seen a rain of articles about a sinking sub, even if the crew would be alive. I don't really know their motives though, mocking Iran military advancements, then a few year later when it is first used, saying that it is a massive threat for the world or whatever, Shahed "Aliexpress hobby drone" and "Chinese copy missiles Saddam scud" are the best examples, their narrative has since changed, this is a Schrodinger Iran military, sometimes it is photoshop and the army s*cks, sometimes Iran is a threat for the world, then claiming drones are made by Aliexpress, then going on saying Ukraine have big trouble of dealing with them (even they intercepted 90% of them)