Stay on whatever visa you’re on -> apply for consular processing -> travel for interview -> enter on green card
So they likely have to wait out the green card process abroad unless they secure a dual-intent visa like an H-1B.
There's also 75 countries that the US has shut down consular processing for so those people may be locked out getting a green card entirely.
You could go the fiancé visa route and stay in status while waiting for the green card.
I think what this policy is trying to avoid is the blanket “you can stay while processing even if you’re not in the country legally”
Wait times to process applications depend on your country of origin and visa type. If you are an H1B from India that was already decades approaching never. Same for Brazil and elsewhere.
And that was before Trump. All that was practically halted.