When using the current installer on a fresh Ubuntu 20.04 (without any packages installed):

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" 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.

this can be fixed by installing the following package:

apt-get install libxkbcommon-x11-0

so either the package can be packed in the installer, or if this is not possible, we should write a pre-request on the installer download page.