Would you give the same advice to someone who was blind or in a wheelchair and asking for reasonable accommodations at work? ADHD is a legally recognized disability in the US, just like other, more visible disabilities. There are a number of accommodations that OP could ask for that an employer would be obligated to provide.
In pragmatic terms, disclosure is probably best kept until after you've been hired somewhere, since discrimination during hiring is commonplace.
No, because those visible disabilities win the favor of juries and get punitive damages. ADHD doesn’t so no lawyer worth anything is even going to take a hard look at the case.
Would you give the same advice to someone who was blind or in a wheelchair
No, I wouldn't. But as fellow ADHD sufferer (who has struggled greatly at times) I would vouch for the parent poster's advice.
ADHD ultimately comes down to coping strategies. At the end of the day you are going to have to develop strategies to focus and accomplish your work.
In this sense it is different than e.g. blindness. A blind person (I'm partially blind, too! fun!) can't cope their way to sight. But an ADHD sufferer is going to have to figure out a way to focus and accomplish work.
I guess if I was already hired I might consider bringing up the disability thing if my employer was doing some weirdo, directly-hostile thing w.r.t. ADHD like banning headphones in an open office. That would be a plan of last resort.
Parent is giving a report from experience and that perspective is worth noting even if it may not be considered kosher by some standards. As such, it should not be dismissed as a bad advice as it deals with the reality of workplaces and not 'world as it should be'.
In pragmatic terms, disclosure is probably best kept until after you've been hired somewhere, since discrimination during hiring is commonplace.