Turns out it's super easy enabling developer options on the latest firmware, F019_R031 at the time of writing.
just plug the eTalk into a computer & open the Engineering Mode app, by dialing either
then just navigate to the bottom, and tap the button that says "打开开发者选项" (lit Open Developer Options in Chinese)
Now go home and open notifications. You'll see a new notification that says "Tap to disable USB debugging."
Tap on it and click the checkbox to fully enable Developer Options.
In the future you can find get back here by going going to Tools & Settings -> Phone Settings -> Developer Options
Right now I haven't been able to get the USB debugging authorization prompt to pop up, but once I do I'll make a new post.