OK, so there's no 'next step' yet, as there's no visa available for him anyway, his PD isn't current. He just needs to sit tight and wait but it'll be at least another year as a rough guess. https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2023/visa-bulletin-for-july-2023.html
And from what you've said he's applied via consular processing, so should expect to be interviewed at his home country consulate when it is current.