Might be different for programmers… my experience is that—broadly speaking—programming ability is inversely proportional to how well dressed you are. I wonder if that is still true, or if I’m just old.

Companies, certainly large ones, prefer people who can communicate and behave professionally, so that would favor well-dressed applicants. If we're thinking nerdy stereotypes: most programmers (by far) don't have to (and can't) solve tricky graph-theoretical algorithms or optimize intricate low-level stuff.

I get a haircut and wear a suit when I interview but am wearing an oversized Star Wars t-shirt while working right now. It’s just putting in the right level of effort at the right time?

There might be a set of people for whom that might be true. There are a lot of people for whom that is not true and, fair or not, they will have an easier time to make things happen in the world

In my experience the worst dressed definitely have more self confidence about their ability, rightly or wrongly

honest question - did that cliche ever apply to women? or non-white people?

i'm well aware of the stereotype but 100% of the time, seen it as a scrubby white guy in a hoodie.