What are some open problems in hyperplane/subspace arrangements, preferably of the combinatorial algebraic topology kind, and where can one read about them? That is, where are they discussed, and where can one learn the necessary background knowledge to understand them properly and in context?

I have been working one one such problem for a while, but I'm ignorant about the big questions, and more generally, interesting problems in this field, and also current trends.

(I'm aware of a few unresolved questions in Richard P. Stanley's *An Introduction to Hyperplane Arrangements* (available online, the unresolved problems are signaled by `[5]`

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