The same novel could be published online and published by a publishing house at the same time, but whether it was feasible or not depended on the requirements of the publishing house. Some publishing houses may require authors to publish on their platform before publishing on other platforms, while others may allow authors to publish directly online. No matter what the requirements of the publishing party were, if the novel was published, there would be no problem in publishing it online. However, if you want to publish it on other platforms, you need to contact the corresponding platform to see if they accept different versions of the same novel.