Menus not exported via DBus, breaking various menu helpers
GIMP version: 2.10.0
Operating System: Ubuntu MATE 18.04 LTS
Package: Ubuntu snap (snapcrafters)
Description of the bug
Utilities that rely on menus being exported over DBus do not work with GIMP 2.10. These include global menus like Ubuntu 16.04's Unity desktop, XFCE and MATE with vala-panel-appmenu, and KDE's menubar feature. More importantly, accessibility tools like the Unity HUD and Ubuntu MATE's rofi-based HUD, which allow keyboard-based keyword search of an application's menus, do not function with GIMP 2.10.
Reproduction
Run GIMP 2.10 on a system that uses a global menu and/or HUD (e.g., Ubuntu 16.04 LTS)
Expected result: Menus appear in top bar, and are searchable through HUD (Alt_L key).
Actual result: Menus appear below the window's title bar, and are not searchable.