When launched from the command line the error thrown is : owncloud: relocation error: /opt/ownCloud/qt-5.6.2/lib/x86_64-linux-gnu/libQt5OpenGL.so.5: symbol ZTV26QOpenGLSharedResourceGuard, version Qt5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference
Steps to reproduce
Launch owncloud from the command line in the latest kubuntu build of 17.10
Error is generated and the application doesn't launch
Server configuration
Operating system: ubuntu 16.04
Web server: Apache
Database: MySql
PHP version: php 7
ownCloud version: 10.0.2.1
Storage backend (external storage): None
Client configuration
Client version: 2.3.3
Operating system: kubuntu linux 17.10
OS language: English
Qt version used by client package (Linux only, see also Settings dialog): 5.6.2 (I think) OS uses 5.9.1
Client package (From ownCloud or distro) (Linux only): Owncloud
Client logfile: owncloud: relocation error: /opt/ownCloud/qt-5.6.2/lib/x86_64-linux-gnu/libQt5OpenGL.so.5: symbol ZTV26QOpenGLSharedResourceGuard, version Qt5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference
Web server error log: N/A
Server logfile: ownCloud log (data/owncloud.log): N/A
I had a problem that could be related to this today by installing owncloud-client on my Linux Mint 18.2 system. You can find more detail here. I also had problem with QT, i was not able to install the client because of unmet dependencies with ocqt562-libqt5opengl5.
$ owncloud owncloud: relocation error: /opt/ownCloud/qt-5.6.2/lib/x86_64-linux-gnu/libQt5Widgets.so.5: symbol ZTI25QOpenGLPaintDevicePrivate, version Qt5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference
On my Ubuntu 16.04 I have: nm -D /opt/ownCloud/qt-5.6.2/lib/x86_64-linux-gnu/libQt5Gui.so.5.6.2 | grep ZTI25QOpenGLPaintDevicePrivate 00000000005c15c0 V _ZTI25QOpenGLPaintDevicePrivate
I just did a fresh install on a fresh system -- that works. Mabye you are stuck in a half - installed state. Then apt-get install -f might help.
Otherwise, a more forcefull way to remove everything and install from scratch is with
apt-get purge $(dpkg -l | grep ocqt562 | awk '{print $2}') then retry the procedure above...