I searched around and found no mention of this, but then found it on Intuit's Mint product blog: https://mint.intuit.com/blog/updates/you-can-now-connect-you...

Presumably, there are more integrations coming but no information from Apple on this. Seems too good to be true that Apple would offer an API to customers that could be hooked up to a self-hosted Actual instance.

Kind of a bummer that they only have Mint support right now, seems quite at odds with Apple's Privacy goals.