Can I transfer my balance to another card?

No, that’s not permitted per the terms and conditions (linked below). You may be able to payoff the account by using a check from the account you’re attempting to use to fund the balance transfer. If you do the check method, you may still have residual interest to pay off the following month. Checks can take a week or more to credit to an account.

https://www.goldmansachs.com/terms-and-conditions/Apple-Card-Customer-Agreement.pdf

Typically, a balance transfer is done by giving the new card issuer the details of the card you want to transfer a balance from. I don’t see anything particular about balance transfers when looking at Apple’s website, but I’d recommend asking your new card issuer what information they would need, and then contacting Goldman Sachs through the Wallet app to get any needed information/confirm that there won’t be any issues on the Apple Card side of things. You might need to get a check from the new card issuer to present as a payment on your Apple Card.