With all the construction at LAX, do flights actually depart from terminal 6, or is there a mile underground hike to a different terminal for departure??

From the rental cars location, take the shuttle but ask the driver what's the fastest way to walk. OTHERWISE you will have to go all the way around the airport. It saves time.

If you're flying Alaska Airlines or Air Canada it's T-6

Departs from terminal 6

I departed from Terminal 6 on an international flight 3 weeks ago.