I found a regression on 9.0.5. Opened an issue about it on github/JUCE, full details there. The problem:
On 9.0.5, since 5bc3927, items in the 1st-level submenu of a PopupMenu can’t be clicked in an AU plugin in Logic Pro. Hovering highlights them, but no response to clicks. Deeper submenus work. The menu is shown with showMenuAsync(PopupMenu::Options{}.withTargetComponent(menu_button)). Adding .withParentComponent fixes it.
There’s no issue in Reaper, AU/VST3 works, standalone also works. 5bc3927^ and 9.0.4 works everywhere.