That's the beauty of Linux Mint... I installed it directly from th Software Manager of Linux Mint. 15 seconds later, it's running perfectly on my HiPDI screen. No command line, no research to do... just playing music!
Yes of course that's why we all start every single gui app from the terminal passing arguments like "--look-nice-in-my-screen". The terminal shouldn't be used to type "chromium --please-run-nice", that should be default, if you pass an argument to start a gui app from terminal it should not be obvious, it should be a special case.
So I don't think that typing "spotify --force-device-scale-factor=1.5" instead of just typing "spotify" is "most efficient way to interact with your computer". And I don't think you should add an argument to an application just to make it usable.
I realized, I have never answered this thread, but this is obviously a bug that should just be fixed by Spotify. There is also another related, not as important, but much more complicated problem. It needs to rescale on the fly when you move the window between screens with different resolution. That probably requires the user to run a different display server, like Wayland or Mir, which is also not supported natively. Both problems are bugs and filed internally in the spotify desktop client bug tracker.