> Supposing I did, the only hamburger menus I can think of contain lesser-important functions of each app

gEdit places almost everything in the hamburger menu; opening and saving files have dedicated buttons but for example find/replace is behind the burger, as is "save as". It may not matter much if you use keyboard shortcuts (ctrl+f is pretty common for find and I never try to look for it in the menu) but one might still expect a GUI to allow its features to be easily accessed without the use of a keyboard. I don't think the mix of a few dedicated buttons and a single hamburger menu is necessarily good for discoverability either.

The Image Viewer puts file management and image rotating in the hamburger menu. Oddly enough, other image editing options are available in a separate editing mode that's accessed via its own dedicated button. Also, although file management features are behind the hamburger menu, for some reason image properties are behind a dedicated button.

In both cases the only reason the hamburger menus aren't more populated is because there just isn't that much functionality in either app to begin with.

Evince (the document viewer) also puts almost everything in the hamburger menu -- although in that case, if a traditional menu bar were used instead of the hamburger, most of its functions would probably only be split between "file" and "view" menus or something along those lines.

I'm not sure if those apps are still Gnome defaults but they're some of the examples of what I'd consider somewhat poorly considered use of the hamburger menu.

Outside of Gnome, the new UI in JetBrains IDEs has switched to hiding typical menu bar menus behind a hamburger menu button. I honestly don't understand that decision at all: the menus are still the same, they just require an additional click to access, and since the selection of available menus is only revealed after clicking the button, you can only start scanning for the menu you're looking for after the reveal. While separate from free software desktop design, the new UI in those IDEs is another example of what I would also consider mobile-influenced degradation of desktop UIs -- and a particularly weird one at that.