There is a Qt5 app (Musescore), that I am trying to get to work on my second Ubuntu computer.
On my main computer (Lubuntu 16.04), Musescore works fine, but on my second computer (also Lubuntu 16.04), it crashes on startup with the message
This application failed to start because it could not find or load the Qt platform plugin "xcb". Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, xcb. Reinstalling the application may fix this problem. Aborted (core dumped)
I have tried a few solutions, (including installing every libxcb* package in the repos), but nothing has changed.
As far as I can remember, this worked fine a few weeks ago, still on 16.04.
ldd /usr/bin/musescore doesn't give any missing liraries: pastebin.
ldd /usr/bin/musescore | grep xcb libxcb.so.1 => /usr/lib/i386-linux-gnu/libxcb.so.1 (0xb1487000) libxcb-dri3.so.0 => /usr/lib/i386-linux-gnu/libxcb-dri3.so.0 (0xaf986000) libxcb-present.so.0 => /usr/lib/i386-linux-gnu/libxcb-present.so.0 (0xaf982000) libxcb-sync.so.1 => /usr/lib/i386-linux-gnu/libxcb-sync.so.1 (0xaf979000) libX11-xcb.so.1 => /usr/lib/i386-linux-gnu/libX11-xcb.so.1 (0xaf936000) libxcb-glx.so.0 => /usr/lib/i386-linux-gnu/libxcb-glx.so.0 (0xaf91b000) libxcb-dri2.so.0 => /usr/lib/i386-linux-gnu/libxcb-dri2.so.0 (0xaf915000)
Edit 2: this is also happening with Notepadqq, with the same error