so get it while you can
Example: If you bought the HHR route for Train Sim World 2, clicking on the “install game” button on Steam for the TSW5 free starter pack (no, you don’t have to install it) will automatically give you the TSW5 version of the HHR route with no further steps; if you’re on PlayStation, you do need to do the same process for TSW4 first.
It is on my list of things to purchase. But since I do not have a lot of time for games I only purchase those that support macOS. Plus then I do not have to worry about fiddling with the game to get it to work.