Fix "Cannot mix incompatible Qt library" on KDE Neon 5.10

By | August 5, 2020

I found that after installing KOrganizer on KDE Neon 5.10, the system experienced error in which I cannot login properly to desktop. The only clue is an error message saying that there is incompatibility in Qt library versions. The solution in my case is by apt-get upgrade:

  1. KOrganizer failed to start.
  2. KDE applications failed to start (Spectacle and Dolphin).
  3. After reboot, it failed to login to desktop. It shows only blank screen (except I still can login to tty).

My specification: Neon 5.10 operating system on a 64bit laptop.
Error Message
Cannot mix incompatible Qt library (version 0x50701) with this library (version 0x50900)
Previously, I reinstalled KDE Neon 5.10 just because of this problem. Once installed, I encountered this problem again! But finally I recognize that I just need to upgrade all packages to solve it:

sudo apt-get upgrade

Note: I didn’t do apt-get dist-upgrade and it’s OK. So in this case, dist-upgrade command is not needed.


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