I know this is pretty old, but I just found a solution, and maybe it could be used by others.
Putting a tooltip directly below the progress panel does not work, but you can wrap it all in a div or span:
<div> <md-progress-linear md-mode = "determinate" value = "value"> <md-tooltip> Hello </md-tooltip> </md-progress-linear> </div>
This way it works fine. They have not found anything yet, and in official discussions this does not seem like a solution.
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