I suspect it is either a noisy motor controller or the transaxle. A defective AC motor controller can become louder over time.

MCFEFE - That's just Plum Quick (?) :) Navitas controller?

Drifting slightly off topic, any recommendations for a battery charge to keep at a second location?

Update from OP: Cart was returned to original dealer. Mechanics there could not find the cause for the whining/grinding noise. The invoice indicated the controller was “computer tested” and an additive was added to the “rear end.” Cart was test driven but they “found no issues.” Verbally, I was told it is safe to drive the cart and if EZGO receives a lot of complaints about noise issues they will investigate and possibly issue a recall. So anyone having the same problem should contact EZGO in addition to complaining to the dealers.

Does it still sound the same to you? Depending on where you live I might be able to bring mine by so we can drive them both and compare.

The sound is the same as before. The same models we have test driven have been completely silent until they reached their higher speeds when road noise is evident. Is your cart the same 2021 EZGO Freedom RXV Elite with 4.2 lithium? The first of these were just manufactured in January, though some of the 4.0 models from late 2020 (still designated as 2021) have been exhibiting similar whining/grinding noises. We have already compared our cart with one of these. Theirs had larger wheels and the seats were different in that our cart has the new thick bench seat and theirs had bucket style seats. The noise emitted was similar on both carts and the other owners have an appointment with The Villages dealer later this month to have this checked out.
If your cart is one of these two models, what type of noise is it making?

Ours is a 2020 4.0 purchased last May. It’s not really making any noise I wouldn’t expect. We have what I think would be normal motor and gear whirring that varies with speed, but is not loud or bothersome. In the first month we had it there was a sound like a piece of sheet metal rubbing on a rotating part, but it went away on its own before I could get it back to dealer.

Okay, the sounds coming from our cart are very different from that. The noise from our cart is a very high pitched, pulsating whining sound with a grinding noise in the background. The only time the cart runs silently is when it is in reverse - except for the backup alarm, of course. After test driving several new carts of the same model at dealerships, we expected silent operation while driving forward, as well, especially at very low speeds on flat streets.
So there’s really no reason for us to compare the carts, though I appreciate the offer. Thanks.

Obviously they are not mechanics...They are just sales people.
It would be easy to find the noise if they were really "mechanics".

I suspect they thought the noise was coming from the transaxle since they installed "an additive". Differential gearsets are cut and honed to mitigate gear whine. No additive will help a poor gearset...You would need a transaxle gearset replacement. A differential whine is not really a problem except the noise is annoying and you paid EZGO for a "silent" transaxle at purchase.

They are obviously just trying to get you to go away. What you fail to understand is that the quiet transaxles are the ones with problems...not the noisy ones. Tell them you want your problem-free noisy transaxle replaced with a quiet problematic one :)