Greetings @KDehren,
This sounds like a permissions issue. As seen in your logs a container bind-mounts the directory /home/karsten-lnx/Desktop/TestProject from your host machine. The container will then run cmake to configure the build, which will result in files and directories being created in /home/karsten-lnx/Desktop/TestProject.
Now for whatever permission related reason, the container can’t create files/directories in /home/karsten-lnx/Desktop/TestProject. I’m not exactly sure why on your PC you have this permission issue, to clarify I don’t get this issue on my setup. I’m not sure if you’re on Linux or WSL or how you have your PC setup/configured. Generally I would say to change the permissions on your directory so that the container can write to it.
This other thread a customer got a similar error and found a way to workaround the permission issues: Qt Template Project not working on Ubuntu Linux
Best Regards,
Jeremias