I have no experience with assistive software but I suppose non-native UI libraries should be using native OS toolkit (e.g. [0][1]) or specific APIs libraries, which targets NVDA, JAWS, Orca and others (this is one of the same idea shared in the one answer on SO [2]). I guess web browsers and other native GUIs just do that behind the scene.

[0]: https://en.wikipedia.org/wiki/Microsoft_Active_Accessibility

[1]: https://en.wikipedia.org/wiki/Microsoft_UI_Automation

[2]: https://stackoverflow.com/questions/65168795/make-non-native...

Edit: IAccessible2 [3] seems to be compliant to both Windows and Linux. Whether Apple AppKit provides specific accessibility-focused UI elements [4]. Flutter has also similar one, it is called Semantics [5].

[3]: https://wiki.linuxfoundation.org/accessibility/iaccessible2/...

[4]: https://developer.apple.com/documentation/appkit/nsaccessibi...

[5]: https://api.flutter.dev/flutter/widgets/Semantics-class.html

On macOS one would create a hierarchy of custom accessibility objects representing the application's state via NSAccessibilityElements: https://developer.apple.com/documentation/appkit/nsaccessibi...