Is the refund advance loan available now?

If the refund advance becomes available it will not be until January 2024.

After January 1 and just when you are ready to file. And only if they offered it to you. You can't self select it. Then you don't get it until AFTER your efile is Accepted by the IRS which is usually late January.
https://turbotax.intuit.com/refund-advance
It says......after IRS acceptance.

And see this FAQ
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-refund/refund-advance/L52Mg0G5u_US_en_US