Thank you michelangelo for the fast response!
Plugins installed:
IR Remote Controller (version from github)
miniDLNA (https://github.com/volumio/volumio-plugins/pull/188)
RemotePi
Touch Display (version from github)
Backup & Restore Data
In case it should be of interest the attributes of /etc/os-release are
lrwxrwxrwx 1 root root 21 Jan 7 2015 os-release -> ../usr/lib/os-release
and the attributes of /usr/lib/os-release are
-rwxrwxrwx 1 volumio volumio 677 Aug 27 15:28 os-release
The content of os-release is:
[code]PRETTY_NAME=“Raspbian GNU/Linux 8 (jessie)”
NAME=“Raspbian GNU/Linux”
VERSION_ID=“8”
VERSION=“8 (jessie)”
ID=raspbian
ID_LIKE=debian
HOME_URL=“http://www.raspbian.org/”
SUPPORT_URL=“http://www.raspbian.org/RaspbianForums”
BUG_REPORT_URL=“http://www.raspbian.org/RaspbianBugs”
VOLUMIO_BUILD_VERSION=“7124eaf0213deb060cebb17ef631669189a6650e”
VOLUMIO_FE_VERSION=“b52b5dfa93e3b26d6f23f09c91a5b90b0a43edf0”
VOLUMIO_BE_VERSION=“273d2050e44b6f5ae901d967e346577f7ad86f2c”
VOLUMIO_ARCH=“arm”
VOLUMIO_VARIANT=“volumio”
VOLUMIO_TEST=“FALSE”
VOLUMIO_BUILD_DATE=“Mon Aug 27 17:21:50 CEST 2018”
VOLUMIO_VERSION=“2.452”
VOLUMIO_HARDWARE=“pi”
VOLUMIO_HASH=“1802c403029d39af3072f40e987e7ba4”
[/code]
EDIT:
One more thing: The system has been set up with 2.452 initially and has not been updated in the past.