This appears to be "sort of" fixed in the latest versions:

openSUSE Leap 15.5 with all available updates installed

Samsung Galaxy S21 ultra 5G latest OS update 8 December 2024

Now when I plug in the USB cable between phone and PC and click the Disks and Devices in the KDE system tray and then Click Browse Files with File Manager, it open a file manager window with a warning message "Could not access device..." and at the same time the phone pops up a dialog asking me whether I want to allow access to phone data. If I touch on Allow, the Internal Storage in the phone appears in the file manager window, but the warning message doesn't go away, although it can be dismissed by clicking on its close button.

A bit clumsy, but usable.

So if you still have a problem, the "solution" seems to be to wait until your Linux distribution supplier updates their file browser and your phone manufacturer updates your phone software.