Now working for me. LInux MInt Ubuntu 16.04 compatibility:
apt-get purge owncloud-client
apt-get autoremove
apt-get autoclean
sh -c “echo ‘deb http://download.owncloud.com/repositories/desktop/Ubuntu_16.04/ /’ > /etc/apt/sources.list.d/owncloud.list”
apt-get update
apt-get install owncloud-client
$ owncloud
owncloud: relocation error: /opt/ownCloud/qt-5.6.2/lib/x86_64-linux-gnu/libQt5Widgets.so.5: symbol _ZTI25QOpenGLPaintDevicePrivate, version Qt_5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference
Waiting for solution 