Finally weekend, could now try piper's proposal but without success.
EDIT: sorry have to try reboot in addition
No success at all. I tried
#Bus 005 Device 007: ID 0bb4:0f25 HTC (High Tech Computer Corp.)
SUBSYSTEM=="usb", ATTR{idVendor}=="0bb4", MODE="0666", GROUP="plugdev"
#SUBSYSTEM=="usb", SYSFS{idVendor}=="0bb4", MODE="0666", GROUP="plugdev"
both of the rules in 51.android.rules and also both commented with and without "GROUP...".
Interesting seems to me, that the phone appears with a double entry as media player in the popup that lists the plugged devices.
The error message is always the same.
mtpfs -l provides me:
Listing raw device(s)
Device 0 (VID=0bb4 and PID=0fb5) is a HTC HTC One M8 (MTP+UMS).
Found 1 device(s):
HTC: HTC One M8 (MTP+UMS) (0bb4:0fb5) @ bus 3, dev 15
Attempting to connect device
Android device detected, assigning default bug flags
Listing File Information on Device with name: (NULL)
fuse: missing mountpoint parameter
Do I have to teach/tell fuse mountpoint params? Where can this be done?