I think you are stuck for the full 24 seconds. But it doesn't say you can't attack or be attacked by creatures and objects on the material plane. I think it is mostly a movement ability and also an anti ethereal monster ability.

Normally, creatures in the Border Ethereal can’t attack creatures on the overlapped plane, and vice versa. When you are in one plane, targeting a creature or object in the other requires the use of a feature or spell that specifically allows it. I don't see anything in the description of Ethereal step that provides this functionality.

Upon reaching 7th level, at the start of your turn, if you aren’t incapacitated, you can choose to magically step into the veil between the planes.

You can move through other creatures and objects as if they were difficult terrain, as well as see and affect creatures and objects on the Ethereal Plane. You take 1d10 force damage if you end your turn inside an object. If you are inside an object when this feature ends, you are immediately shunted to the nearest unoccupied space that you can occupy and take force damage equal to twice the number of feet you moved. This feature lasts for a number of rounds equal to your Intelligence modifier (minimum of 1 round).

You can use this feature once. Beginning at 15th level, you can use your Ethereal Step feature twice between rests. You regain all expended uses when you finish a short or long rest.

I can't tell if the intention was to be able to end the effect early, but the way it is written, it seems like you are stuck there for the duration as DxJxC says.

Other than the name, nothing about ethereal step' s effect suggest they actually went to the ethereal plane/border ethereal. It says "veil between the planes." Which could (and I think does) mean they are between the material and border ethereal and able to interact with both.

And as I pointed out, it doesn't say you can't interact with the material plane, unlike etherealness for example.

I would suggest that the Border Ethereal is the veil between the Material Plane and the Etheral Plane (Deep Ethereal). We have to be careful deciding that you can do something just because no rule prevents it. That logic only holds up if the default assumption is that you can do so. Otherwise, we run into the Air Bud paradox. The only thing the feature specifically allows is interaction with the Ethereal plane.

That's the way I see it anyway. You and I are obviously looking at the same rules and just reaching different conclusions.

I've always assumed it meant what Dx laid out. "Veil between the planes" is an imprecise location that could mean anything. The fact that they later mention the Ethereal Plane by name lends some credence to the idea that these two locations are not the same thing, and that the planes you are between are the initial plane and the Ethereal. There's also the way the feature works - it is clearly a combat feature (references to turns and rounds) that is intended to be used multiple times a day. It seems unrealistic that most of the time this class would be using it to effectively take itself out of combat for four turns except in the rare case that an enemy has fled to the Ethereal Plane.

So ultimately I'd read it in the manner that allows it to actually be useful on the level that most other class features are.

LOL I am 100% wrong. I asked Matt Mercer just now and he answered.

Nice.

Quote from TexasDevin >>

We have to be careful deciding that you can do something just because no rule prevents it. That logic only holds up if the default assumption is that you can do so.

 We also have to be careful inferring that a rule does something it doesn't say. The default is that you can attack creatures on the same plane as you, and the feature did not by its wording send you to a different plane.

I know this is settled, just wanted to say this as it applies in other ruling discussions.

I disagree with your analysis there, but you're right it is settled.