Today I upgraded the client to the 2.4.0 version and I got this error
This application failed to start because it could not find or load the Qt platform plugin "xcb"
Available platform plugins are: linuxfb, minimal, offscreen, xcb.
Reinstalling the application may fix this problem.
The problem is on the qt5 version. In fact
ownCloud version 2.4.0 (build 8911)
Git revision 9a1f736e306f135628e77bca5c1edeed8b1f3736
Using Qt 5.6.2, built against Qt 5.6.2
Using 'OpenSSL 1.0.1f 6 Jan 2014'
but the qt5 version of Ubuntu 14.04 is still 5.5.1
I do not know how to downgrade, nor updating qt5 on Ubuntu. How can I fix it?