I see this when I run a snap, and it is not causing a problem for me. You said you are using AppImage, but this message is clearly coming from snap given the path in the message. I do not see this when running the AppImage. I did a little research, and it is not clear to me if something should be done. It can be used to provide a temporary directory, but Qt QStandardPaths still finds a temporary at /tmp on my system.