ok, i found it
i needed to add my phone ID to ~/.android/adb_usb.ini
(see here ā unfortunately only in german)
ā> find it via ālsusbā (run it, disconnect the phone, run it again ā you see which ID is missing, that was the phone ;))
add ā0xā + the first 4 characters of the ID (before the colon)
so, e.g. ā0x1234ā to the file (create it if it does not exist)