Does Dunebreaker proc if I have 3 cards in hand and I have 2 left after playing it?

Ruling

Yes, Dunebreaker will enter ready in this scenario.

Reasoning

According to the card text for Dunebreaker: "If you have two or fewer cards in your hand, I enter ready."

This is a conditional passive ability (Rule 364.3). For a unit to enter ready based on a hand-size condition, that condition must be met at the moment the unit enters the board.

Sequence of events:

1. Playing the card: You start with 3 cards in hand. You play Dunebreaker.
2. Paying costs: You pay the energy cost to play the card. Your hand size is now 2 (3 cards minus the Dunebreaker you just played).
3. Entering the board: Dunebreaker enters the board. At this exact moment, the game checks the condition: "Do you have two or fewer cards in your hand?"
4. Condition Check: Because you have 2 cards remaining in your hand, the condition "two or fewer" is met.

Note: I could not fully verify this ruling against the retrieved rules.