I've recently been playing around with Blender (following this tutorial series). In Part 4 of the Level 1 series, the host Andrew Price is teaching about loop selects which very simply is holding down Alt while clicking on a vertex. The issue wasn't working for me though I found quite a few other users experiencing the issue.
The most common fix was when people had three button mouse emulation enabled (a common setting people turn on when using laptops or Macs). I checked this and it wasn't my issue.
I'm running the Cinnamon desktop environment on Fedora (though I'm sure this would universally apply to all Cinnamon instances), which has a "convenience" feature that allows you to hold down a modifier key inside a window to move or resize it. By default this is Alt.
To change this open up the
System Settings app, navigate to the
section, choose the
Behavior tab and change the setting of
Special key to move and resize windows to
Disabled. Bam, problem solved loop select is
working like a charm.