Reading a book - especially long-running webnovels which can have hundreds of chapters - is a commitment. You want people to invest the most important thing they have: their finite living time.
To go with a somewhat helpful comparison: Think of your first chapter as a movie trailer. Your blurb, tags, and cover is the youtube thumbnail. They will determine whether the reader clicks on the trailer and watches it for 3 minutes or not. Your first chapter is the trailer itself.
So what is important about a trailer? Do they need to show the entire story? Do they have to explain all the world and character's backgrounds? No. The most important thing is a rough outline and a lot of atmosphere. A movie trailer is a promise to the viewer: if you like the funny lines, there'll be more like this in the movie. If you liked the explosions, there are bigger ones in the movie.
Both a movie trailer and your first chapter are a promise to the consumer: If you invest your time into this, you'll get a lot more of this. So start with a defined atmosphere in your chapter, a clear central theme, and the foundation for a conflict. It doesn't have to be the final main conflict, but there should be some sort of conflict in your first chapter. Conflict and the resulting change make a story interesting.
Staying with movies, think about the beginning of a James Bond movie. It's an action movie, so they often start with an action scene, before they slow down to introduce the actual plot of the movie, before delivering on the promise of "even more action". If you have a thriller or detective story, you often start with some kind of crime and suspense. If you write a more internal story, introduce some outlined themes like "mortality".
In the end, your first chapter needs to achieve two things:
(1) Promise the reader "more of the same". For that, you have to clearly define what that "same" is and present it to the user. So it doesn't need to be a big action fight scene, or a giant hook, but something that fits your story and themes.
(2) Make clear to the reader that your story is worth their time: make sure grammar and flow are as good as possible, your central theme is clearly communicated, you don't give "too much information" to the reader, etc.
So going by this: introduce the central theme of your story (not necessarily the central conflict), the overall atmosphere, and give some outlines or questions to the reader...