The network ups tools are designed to drop root privileges before opening the serial port to communicate
with the ups.
Thus the nut package has to be told during compile time as which user and group it has to open the serial
port.
Unfortunately it seems that nut was compiled to open the port as nobody/nogroup.
This results in two problems:

 - The group nogroup does not exist ("getgrnam() failed: group nogroup does not exist" is shown when trying to start nut)
 - The serial terminals /dev/ttyS0 etc. are owned by root/uucp. Thus nut should be compiled to run as group uucp.