Extract from a Writers Helping Writers article:

What’s the right ending for your novel? This isn’t a simple question to answer, because there are many factors to consider. But the first thing you want to think about is the story’s genre.

Let’s take a simple example. Suppose your story centres around a startling event like a murder. Should the murder be solved? If you’re writing a cosy mystery, yes. If you’re writing a political thriller or a police procedural, you probably have to solve the murder, but it’s not mandatory. If you’re writing a contemporary or experimental novel, you might not present any concrete answers about the murder—you might use the event to explore other questions.

So if you’re struggling to identify what your ending should be, the first place to look is the genre expectations. All stories provoke curiosity and raise questions. That’s what keeps the reader’s attention through hundreds of pages. Your genre is characterised by where you direct that curiosity. What does your reader care about most? Solving the puzzle and restoring order? Studying relationships where there are no easy answers? Picking apart the structures and flaws in society and our power systems? Identify your ideal reader’s pleasure and what the genre implicitly promises, then use your ingenuity to fulfill it in an original way.

What Do All Good Endings Have?