Hi,
I have a blog powered by Hugo. I deploy the bog on Github Page, I have followed the Hugo documentation page on 404 Custom page. But As I can see, it is not working on my blog when it is deployed.
Generate the project locally and then simply copy the 404.html from the language directory under /static/.
The staticDir lives outside Hugo’s Multilingual Mode, therefore a 404.html under the root of /static/ will be served under the root of the domain without having to use any shell command during deployment.