Hey, I checked the USB settings (drivers) in the Device Manager in the Control Panel of my Windows 10 PC. I pressed also “Search for new hardware”. It didn’t bring up any visible change but …
… just now I plugged in the cable, switched on “File transfer” and have indeed access to the internal device memory and the SD card for the first time, read and write. I don’t know why, or what has changed (or if anything has changed at all) but now it works as I always expected.
Will check this on my Linux machine this afternoon.