How to achieve NSPopupButton "grouped form" style using AppKit?

How does one achieve the "grouped" style controls without SwiftUI, using only AppKit? I've played with combinations of bezel styles and other properties, but cannot get it to fit that style.

This is the Settings app on macOS, which uses SwiftUI form with .formStyle(.grouped). But internally, SwiftUI uses regular AppKit controls, including NSPopupButton. Also, the modern print panel fakes/recreates the form style fully in AppKit:

Private API is fine too, I have just not been able to find it.

For technical reasons I will not get into this question, SwiftUI cannot be used.