Cannot mix incompatible Qt library (version 0x50501) with this library (version 0x50201) - qt

Question

I have installed Shadowsocks-Qt5 within the code sudo apt-get install shadowsocks-qt5 in terminal, and then I can find the launch icon by searching, but it won't open when I click the icon. Then I tried to use terminal to open it, but the error comes out as below:
~ ss-qt5
Cannot mix incompatible Qt library (version 0x50501) with this library (version 0x50201)
[1] 8875 abort (core dumped) ss-qt5
I searched many answers but no one work. I think the key may be the default Qt library, but I don't know how to set default Qt library, the system on my computer is Ubuntu 14.04 LTS.
How to solve this problem?

Answer 1

I just had this error when attempting to run Qt Creator after doing a system update. For me, I was attempting to run Qt Creator 4.10.0-rc1 (based on Qt 5.13.1) that I had manually installed to ~/Qt along with Qt 5.13.0, and my system has Qt 5.12.2 installed.
I was getting the following error:
Cannot mix incompatible Qt library (version 0x50c02) with this library (version 0x50d00)
Doing an strace when running qtcreator.sh revealed that it was attempting to load plugins from the system directory. I finally discovered the culprit was the environment variable QT_PLUGIN_PATH was set (in my case to /usr/lib64/qt5/plugins:/usr/lib64/qt5/plugins/kcms).
After unsetting this variable, Qt Creator started up and worked.

Answer 2

After so many months of trying to fix this issue, this helped me.
sudo apt install qt5-style-plugins.

Answer 3

I was facing a similar issue, and even after 4 hours of debugging, I got nowhere. Finally, I found the following way to keep separate Qt versions, posting here so that other people find it.
Suppose you installed Qt in ${QtRoot}, extend the PATH and LD_LIBRARY_PATH:
export PATH=${QtRoot}/bin:${PATH}
export LD_LIBRARY_PATH=${QtRoot}/lib:${LD_LIBRARY_PATH}
You can make a wrapper function / script to manage separate Qt installations like this:
QtVersion=5.12.8
QtRoot="/scratch/Qt/${QtVersion}/gcc_64"
export PATH=${QtRoot}/bin:${PATH}
export LD_LIBRARY_PATH=${QtRoot}/lib:${LD_LIBRARY_PATH}
After running this your application will likely run fine.