He is not banned. He cannot get an appointment at the embassy in the near term and obviously assumes that this situation will persist.<p><i>"I now can’t get an embassy appt until 2022! citing being ‘understaffed’<p>It turns out, during COVID the embassy operated a week on, week off schedule so now they’re over a year behind on appointments.<p>They will give emergency appointments, but I’ve tried and I apparently don’t qualify - though there’s no guidance on what does qualify either."</i>
Dude has been on O1 visa for 7 years and never considered filing for Green Card. For anyone qualifying for O-1 visa, self-filing as EB-1 or EB-2 is absolutely possible, why didn't he? The US immigration system is broken and capricious, as permanent resident it's much less painful. Let's just call his present predicament a self-inflicted wound.
The pandemic really messed a bunch of stuff up for a lot people in this situation. I don't think it's malicious, or even incompetence. They just had to scale back staff dramatically at foreign embassies. And isn't UK still having virus problems? In any case, he's certainly not "banned." Hopefully he'll be able to get a visa appointment sometime soon.