Figured out how to increase the font scale – and smoothen out the fonts – in the Spotify Linux client.
It goes something like this:
$ /usr/lib64/spotify-client/spotify --enable-font-antialiasing --force-device-scale-factor=1.25
Much the same arguments as from Chromium. 🙂
You can set the parameters on the application launcher by editing /usr/share/applications/spotify.desktop
Exec=sh -c "spotify %U --enable-font-antialiasing --force-device-scale-factor=1.1"
Make sure you restart gnome-shell – it seems to otherwise cache entries.
This trick even works for the WordPress client app for desktop!