I'm working out of Linux Mint, just wanted to make a note to the community that if you're having troubles with using Alt + Left Click for selecting edge loops, it likely has to do with your settings. In Mint, I had to do this to get mine to work:
Super Key on Keyboard (Windows Key) > type "settings" > click "system settings" > scroll down to preferences > click "Windows" > Go to the "Behavior" tab at the top > Under "Moving and Resizing Windows", disable "Special key to move and resize windows"
This should fix the issues on Linux Mint. If you're running another distro, I would imagine the process is similar but not the exact same. It may be under your keyboard shortcuts too if you're in another distro. Hope this helps!
