First, go to your library and click on TTEOTS so you see the bar at the bottom like this:

Second, click on the cogwheel beside launch so you see this window pop up:

Then, click on manage so you are met with this:

Click on "Switch to another version" so that you are met with this final screen:

Finally, click on "version 6" which was released February 11 if you are playing on Windows. My assumption is that the different types of operating systems will have their respective versions listed in this window, so you should be able to redownload the old versions the same way on mac and linux. Hope this helps!