qt.qpa.plugin: Could not load the Qt platform plugin "xcb", no Qt platform can be initialised, but "Available platform plugins are: xcb, eglfs......"

Question

I am trying to run a script that creates a UI, using Qt and opencv. However, this is an odd error that I got

python3 dashboard.py 
QObject::moveToThread: Current thread (0xaffdf0) is not the object's thread (0x552f790).
Cannot move to target thread (0xaffdf0)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

Aborted (core dumped)

This is the output from ldd-ing libqxcb.so

ldd libqxcb.so 
    linux-vdso.so.1 (0x00007ffdbfbf5000)
    libQt5XcbQpa-ca221f44.so.5.15.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5XcbQpa-ca221f44.so.5.15.0 (0x00007f32102a5000)
    libfreetype-c0e61f0c.so.6.14.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libfreetype-c0e61f0c.so.6.14.0 (0x00007f320ffd9000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f320ffa9000)
    libQt5Gui-ba0a2070.so.5.15.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5Gui-ba0a2070.so.5.15.0 (0x00007f320f6a1000)
    libQt5Core-39545cc7.so.5.15.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5Core-39545cc7.so.5.15.0 (0x00007f320ef9c000)
    libGL.so.1 => /lib/x86_64-linux-gnu/libGL.so.1 (0x00007f320ef14000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f320eef2000)
    libX11-xcb-69166bdf.so.1.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libX11-xcb-69166bdf.so.1.0.0 (0x00007f320ecef000)
    libxcb-icccm-413c9f41.so.4.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-icccm-413c9f41.so.4.0.0 (0x00007f320eae9000)
    libxcb-image-e82a276d.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-image-e82a276d.so.0.0.0 (0x00007f320e8df000)
    libxcb-shm-7a199f70.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-shm-7a199f70.so.0.0.0 (0x00007f320e6d9000)
    libxcb-keysyms-21015570.so.1.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-keysyms-21015570.so.1.0.0 (0x00007f320e4d5000)
    libxcb-randr-a96a5a87.so.0.1.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-randr-a96a5a87.so.0.1.0 (0x00007f320e2be000)
    libxcb-render-util-43ce00f5.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-render-util-43ce00f5.so.0.0.0 (0x00007f320e0b8000)
    libxcb-render-637b984a.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-render-637b984a.so.0.0.0 (0x00007f320dea2000)
    libxcb-shape-25c2b258.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-shape-25c2b258.so.0.0.0 (0x00007f320dc9c000)
    libxcb-sync-89374f40.so.1.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-sync-89374f40.so.1.0.0 (0x00007f320da93000)
    libxcb-xfixes-9be3ba6f.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xfixes-9be3ba6f.so.0.0.0 (0x00007f320d887000)
    libxcb-xinerama-ae147f87.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xinerama-ae147f87.so.0.0.0 (0x00007f320d682000)
    libxcb-xkb-9ba31ab3.so.1.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xkb-9ba31ab3.so.1.0.0 (0x00007f320d459000)
    libxcb.so.1 => /lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f320d42f000)
    libXext.so.6 => /lib/x86_64-linux-gnu/libXext.so.6 (0x00007f320d41a000)
    libX11.so.6 => /lib/x86_64-linux-gnu/libX11.so.6 (0x00007f320d2dc000)
    libSM.so.6 => /lib/x86_64-linux-gnu/libSM.so.6 (0x00007f320d2d1000)
    libICE.so.6 => /lib/x86_64-linux-gnu/libICE.so.6 (0x00007f320d2b4000)
    libxkbcommon-x11-c65ed502.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxkbcommon-x11-c65ed502.so.0.0.0 (0x00007f320d0a5000)
    libxkbcommon-71ae2972.so.0.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxkbcommon-71ae2972.so.0.0.0 (0x00007f320ce64000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f320ce5d000)
    libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f320cc44000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f320caf6000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f320cadb000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f320c8ed000)
    libgthread-2.0.so.0 => /lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f320c8e8000)
    libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f320c7b2000)
    libbz2-a273e504.so.1.0.6 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libbz2-a273e504.so.1.0.6 (0x00007f320c5a1000)
    libpng15-ce838cd1.so.15.13.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libpng15-ce838cd1.so.15.13.0 (0x00007f320c374000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f3210533000)
    libGLdispatch.so.0 => /lib/x86_64-linux-gnu/libGLdispatch.so.0 (0x00007f320c2ba000)
    libGLX.so.0 => /lib/x86_64-linux-gnu/libGLX.so.0 (0x00007f320c286000)
    libxcb-util-4d666913.so.1.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-util-4d666913.so.1.0.0 (0x00007f320c07f000)
    libXau-00ec42fe.so.6.0.0 => /home/aevas/Desktop/pyenvs/newpy39/lib/python3.9/site-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libXau-00ec42fe.so.6.0.0 (0x00007f320be7a000)
    libXau.so.6 => /lib/x86_64-linux-gnu/libXau.so.6 (0x00007f320be72000)
    libXdmcp.so.6 => /lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f320be6a000)
    libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007f320be61000)
    libbsd.so.0 => /lib/x86_64-linux-gnu/libbsd.so.0 (0x00007f320be49000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f320bdd3000)
    libmd.so.0 => /lib/x86_64-linux-gnu/libmd.so.0 (0x00007f320bdc4000)

pip list, grabbing only the opencv and qt stuff

opencv-python           4.5.5.62
PyQt5                   5.15.6
PyQt5-Qt5               5.15.2
PyQt5-sip               12.9.1

I have also consulted these links, but to no avail:

1. https://github.com/Yuliang-Liu/Curve-Text-Detector/issues/11

2. https://forum.qt.io/topic/93247/qt-qpa-plugin-could-not-load-the-qt-platform-plugin-xcb-in-even-though-it-was-found/65 (done all the sudo apt-get install already)

3. https://unix.stackexchange.com/questions/338519/how-to-install-libxcb (i have also performed the required sudo apt-get installs)

4. How to fix the error "QObject::moveToThread:" in opencv in python? (pip doesn't let me install an older version of opencv-python)

5. https://www.programmersought.com/article/20797211182/ (also about downgrading opencv, which i am unable to)

6. Removing the "qt" folder, from the "cv2" installation from python site packages seems to make it work. However, this crashes other things that rely on opencv_python.

Answer 1

i just install the old version opencv-python==4.3.06. by use:

pip uninstall opencv-python

pip install opencv-python==4.3.06

after that. the qt error disapear.

if u can not use pip to uninstall.may be you used the conda to install the cv?