From package testing Qt 6.5-rc.

When I first tried to install the version of Qt for testing, the already existing installer in my Qt folder was unable to start, since it told me another version was already running. But I had no other version running. It told me to restart there system, but I got the same message after rebooting my machine. The work-around was to either quit Qt Creator, or kill the offending process in the terminal. Since I choose to download a new version of the installer from qt.io, I'm not sure which version of the installer I had from before, but it's probably not more than 6 months old. See screenshot.