When run in the GHA environment, there is no console attached, so Qt's stderrHasConsoleAttached() returns false and the entire test report is lost. Set QT_ASSUME_STDERR_HAS_CONSOLE=1 to override the detection, as documented in Qt's qlogging.cpp:
if (qEnvironmentVariableIntValue("QT_ASSUME_STDERR_HAS_CONSOLE"))
return true;