Hello, when I connect my mobile (Android) with my PC with a cable and via usb, dolphin and gwenview tell me "Unbekannter Fehlercode 150 Unspezifizierter Fehler Bitte senden Sie einen ausführlichen Problembericht an https://bugs.kde.org." In the past I had already problems to connect via MTP but sometimes it worked.
Does this still happen with newer versions of Dolphin? The MTP support has since been improved & the problem might have been fixed.
No. It works now. :-)
Great, I'll close this report then. Thanks for reporting the bug!