A GalaxyS5 is not accessible with 'adb devices' because /dev/bus/usb/*/* lacks
the proper permissions.

kernel: usb 1-3: new high-speed USB device number 34 using ehci-pci
kernel: usb 1-3: New USB device found, idVendor=18d1, idProduct=4ee7
kernel: usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
kernel: usb 1-3: Product: SAMSUNG_Android
kernel: usb 1-3: Manufacturer: SAMSUNG
kernel: usb 1-3: SerialNumber: 4536a2f1
mtp-probe[28143]: checking bus 1, device 34:
"/sys/devices/pci0000:00/0000:00:12.2/usb1/1-3"
mtp-probe[28143]: bus: 1, device: 34 was not an MTP device

Google has a few hits for 18d1:4ee7, it would be nice if one must not manually
fiddle with udev rules files.

This breakage was introduced in the last days/weeks. Either some package is now
broken. Or a change I did manually months ago to some *.rules file was
overwritten. I can not remember if I actually did anything to allow usage of
'adb'.

Switching from 'Charge only' to 'MTP' or 'PTP' does allow both MTP and adb.