Ubuntu thinks Windows key is right super

There indeed appears to be a discrepancy between the standard keyboard layout definition you use and your physical keyboard. Your (only) Super key appears to emit keycode 134 rather than 133, so by default is mapped to Super_R rather than Super_L.

Modifying a keyboard layout involves editing source files. There is, however, an easy way to have your Super key reveal the Activities overview without changing more fundamental configurations. Issue the following command to have Super_R trigger the overview rather than Super_L:

gsettings set org.gnome.mutter overlay-key 'Super_R'

You can reset to the default setting by changing set by reset and leaving out 'Super_R'.