For what it may be worth, Qt and MacOS Tahoe have a rather long list of issues due to Apple's Liquid Glass rendering. You can try setting UIDesignRequiresCompatibility in the info.plist to YES to see if that corrects the issue. Basically, just lets you know that Liquid Glass/Qt is the issue.
See
Qt on macOS 26 Tahoe and
UIDesignRequiresCompatibility for more information.