I hate using my Qt account whenever I install Qt Creator on any public computers, because Installer automatically stores the login credentials on computer. Once stored, I need to manually delete them later on.
Whilst installing Qt Creator via offline installer, I noticed that installer does not prompt for login whenever there is no internet connectivity. You can simulate this by configuring invalid proxy configuration within the Qt Creator installer.
It's quite straight forward. Click on settings button, and configure 0.0.0.0 as the proxy.
After this you can proceed to install Qt Creator without having to worry about the Qt Account login.
It seems above trick does not work with Qt Creator 4.15 (at-least on Linux). Qt Creator installer checks for network connectivity at startup. I use below command to override.
sudo bash -c "http_proxy="http://localhost:0" ./qt-creator-opensource-linux-x86_64-4.15.0.run"
Alternatively, you can disable internet on your computer before starting the installer.