You probably haven't heard of this because it is not a coup. Basically, there is an ongoing project where Erdoğan wants to split european part of the Istanbul in half and run a canal through it. The project is called "Kanal Istanbul Projesi", you can search it up yourself as well. 103 retired admirals recently posted a text over social media, regarding the project and how it may oppose Montreux Convention which gives Turkey control over the Bosporus and Dardanelles straits. Since it was posted by old army people, and it opposes the government, the government and their media straight up jumped on the "it's a coup" train. In reality, there is no coup and some people are just trying to strenghten their legitimacy by acting like they're protecting the motherland.