"Sign In" icon on the main page is a "Logout" pictogram
When I first arrived on the main page of the project, I wanted to connect with the account I just created. I looked for an icon like the icon below to log in.
But instead, the icon I can find in the top-right is something like
Some other website also seems to adopts something more verbose with some text in the top-right like "Sign In / Sign Up" or "Sign In / Register", it might be an interesting proposition to explore too in term of implementation.