Hopping Linux distributions, I came to Ubuntu 21.04, and one of the first things I do is install Qt manually. I have described the process in a previous blog post on Linux Mint, and it is the same for Ubuntu. Except for a tiny detail. On Ubuntu, the bundled QtCreator immediately crashes and triggers a "Send Diagnostic" dialog.

$ /opt/Qt/Tools/QtCreator/bin/qtcreator
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.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, 
xcb.

The fix is simple.

sudo apt install libxcb-xinerama0

I hope this helps. Thank you for reading.