[jeffreyH (OP)]

A gravitational field makes free fall equivalent to an inertial frame. Can the same principle be applied to whatever drives the accelerated expansion of the universe?

[Halc]

Pretty good question if you ask me.  Yes, it is equivalent in that like gravity, any acceleration is locally undetectable.  Expansion itself is completely inertial and requires no force/dark-energy at all.  But accelerated expansion does.  You mention acceleration in your post, but not in the title.

[jeffreyH (OP)]

You mention acceleration in your post, but not in the title.

That was on purpose.

[Bored chemist]

Yes, it is equivalent in that like gravity, any acceleration is locally undetectable.

Sat on my chair, and watching the springs compress, I can detect local gravity.

[yor_on]

Maybe?

you could take a look at this one. https://phys.org/news/2017-03-expansion-universe-dark-energy.html It puts a different 'spin' on the acceleration.