I am lucky that my daughter had Obamacare when she had inpatient stays. There is also a nearby hospital with a psych ward that she went to. All were very short term stays though, less than 30 days. I think her insurance only paid for 30 days max each stay. She is doing well now at 39, and has a very part time job that enables her to buy insurance. But she hasn’t needed a hold for some time now as her meds have kept her stable since 2019.
I wish you luck sorting out the rules for your brother.