I may be blind or stupid, but I'm not able to find the option to turn my Audacious 3.9 (on Linux Mint Cinnamon Desktop) into the dark theme as seen on here:
Can someone help me?
You won't find an option for this since Audacious simply uses your global GTK theme.
If you configure Cinnamon to use a dark theme, Audacious will use it as well.
Heroes don't always wear capes!
Thank you very much. Simple but effective!