If the track says mono on the left it is mono and there is no debate.
If the track says stereo on the left and you want exact information on how much the two channels are alike (“correlated”), try the “rjh-stereo-tool” from https://forum.audacityteam.org/t/karaoke-rotation-panning-more/30112/1 . It is a Nyquist plug-in. Please see here for how to install Nyquist plug-ins: http://wiki.audacityteam.org/wiki/Download_Nyquist_Plug-ins#install .
Choose the “2-D Stereo Toolkit” from the Effect Menu then the “Analyze” option.
If you prefer a simpler test, click in the name of the stereo track and choose “Split Stereo to Mono”. Click in one of the Track Control Panels where it says “Mono” then choose Effect > Invert from the menu at the top of the screen. This turns the waveform of that track upside down.
Now press Play. If you get silence (no green dancing bars in Meter Toolbar), that means the stereo track that you split was “dual mono”, that is the same content is in the left and right channels. When you make both channels into mono tracks, invert one of them and the content of both tracks is the same, then the inverted track will exactly cancel out the other track, resulting in silence.
Gale