I don't know why but it seems Alt+LMB is not working for edge loop selection in blender 2.80. Is it a bug? Or is there's a new shortcut for that?
If you are using Linux Mint this will be an issue as Alt is used for moving and resizing windows.
Go to System Settings > Windows & then go to Behavior tab. Inside there you'll see Special key to move and resize windows and set it to Super and Alt + LMB will work just as fine.
As said by morph3us, you can use Double Click on edge for the edge loop selection in edit mode, for Blender 2.8.
With default preferences (i.e. when you do Load Factory Preferences):
- You can select edge loop by Alt + Left Click on desired edge.
- Shift + Alt + Left Click for multiple edge loop selection.
With modified preferences(i.e. Input > Emulate 3 Button Mouse checked):
- You can select edge loop by Double Click on desired edge.
- Shift + Double Click for multiple edge loop selection.
None of the above works for me in blender 2.90.1.
When I press Alt, the bottom of the window indicates that I should left click to loop select, but when I click, nothing happens.
Alt+Doubleclick = nothing, Alt+Shift+Doubleclick = nothing, Shift+Alt+Left Click = nothing.
It turns out it's my operating system (Linux Mint) that uses the Alt key for window operations. I used the solution where I re-assign Alt to the Super (Windows) key in the operating system, and now Blender works.