If I uninstall Audacious, plugging in a USB drive or SD card will open Dolphin when I click “Open with file manager”. I reinstall Audacious, that opens instead of Dolphin. My laptop started doing this recently, I can’t find a solution online. The USB drive/SD card will mount, though. I shut off Audacious and open Dolphin and can access the USB drive or SD card.
Since you mentioned “Dolphin”, I will guess that you are using KDE. However, it is best to clearly state that when you post.
Try:
Configure Desktop → Applications → Default Applications → File Manager
That should allow you to select your preferred file manager.
**That fixed it! Thanks! **