Comment # 5 on bug 907387 from Stanislav Brabec

Regarding the permissions to serial UPS:

There was a hack in the sysv init script: It extracted serial device name from
the configuration and changed its permissions.

case "$PORT" in
/dev/ttyS* )
chown $UPS_OWNER $PORT

Adding dialout group to UPS device is an ugly hack. And dangerous, because it
allows any user to manipulate with UPS. dialout group should be used to allow
access to a modem/serial port to any user.

More correct would be creating and udev/systemd rule configuring serial port as
an UPS device port.