We'd love to support macOS but sadly we don't have a Mac available for building/testing right now 😕
Our current codebase should indeed be 99% compatible with macOS though (our rendering engine supports Vulkan, which means Outer Wonders should be compatible with macOS/Metal using MoltenVK), so once we have a Mac available for testing we'll work on proper support for macOS 🙂
In the meantime you may want to try running the Windows version using Wine if your Mac supports it.