When I select "Git" in Source Code Management and supply the public repository URL, the one (linuxacademy) you used in the training session, it is throwing error "Failed to connect to the repository". Please refer the image. Please help me to understand what is going wrong here ?
It appears that the URL that you have supplied to the project is incorrect. The URL should end in .git shown below.
One other issue that can manifest itself in the error that you are seeing is that git is not installed on the node. If git is installed in the Global Tools configuration I would validate the URL you are supplying to the project.