Hi @paulsvang,
I have exactly the same problem as you.
Did you found a way ?
I have an other idea, but sounds heavy :
1- Create a post with the standard API
2- Get the ID after the creation
3- Use the extension ACF TO REST API and do an update of the initial post just to fill up ACF fields.
We can exchange about this together if you want (as we are in the same boat apparently ^^)
