Just for Windows platform:
#if PLATFORM_WINDOWS
FString LogFile;
FOutputDevice* OutputDevice = FGenericPlatformOutputDevices::GetLog();
if (OutputDevice != nullptr)
{
FOutputDeviceFile* OutputDeviceFile =
static_cast<FOutputDeviceFile*>(OutputDevice);
LogFile = OutputDeviceFile->GetFilename();
}
#endif // PLATFORM_WINDOWS