Romero’s Night of the Living Dead is in the public domain as well.

You can find it in the Internet Archive here: https://archive.org/details/night_of_the_living_dead

It could be an issue with the codecs (browsers are usually pretty limited in what they support). You could try to use a client like Jellyfin Media Player instead. It bundles libmpv, so it plays almost any video format there is.