How features are integrated in between Stack Exchange forums?

Question

Recently Stack Overflow introduced dark mode preference option, but it isn't available here, at Unix & Linux.

How it works for it be provided at the other forums?

Answer 1

According to How do I enable dark mode on other sites in the network?, it is not yet available outside of Stack Overflow:

Dark mode is currently in beta and only available on Stack Overflow. You cannot enable it anywhere else at this time.