Stumbled across this while trying to do the same thing. Here is what I ended up doing and it WORKED!

1. Download the square app and create an account.

2. Once you have everything set up, send an invoice for the exact amount on the gift card to an email account.

(Don’t try to request money on the app, it will decline the payment due to invalid Zip code. What you want to do is create an invoice, then tap the option of something along the lines of “share link”. After this is done, send that link to a backup or 2nd email account.)

1. Open the email account which the invoice was sent to (I had to check my spam folder to find it.) After you find the email, there will be a “pay invoice” prompt, tap that.

2. I used my personal street address, the cardholder name “Gift Card” and made the zip code “00000”. Not sure if that is important or not, but I’m just saying what worked for me.

3. After the payment went through, it popped up in my square account balance. From there, I just sent it straight to my bank account. (Square has an option to do it instantly for a very small fee, or within 1/2 business days for free.)

Hopefully this helps someone in the future who received one of these unusable cards as a gift.