Replying to myself with more info:

This is proving exceptionally hard to search the web for, so apologies if this is out of date, but it seems the answer was “no, and it never will be, so stop asking” as of 2018: https://twitter.com/danielfore/status/991836014070022144

Was this from before Elementary was positioning as the MacOS replacement? I can’t be the only one who thinks the global menu is one of the MacOS interface’s killer features.

I understand why it’s been hard under the X paradigm, but those crazy dbus people are pushing entire application interfaces through IPC now.