This is a difficult topic to talk about, since my interviews are all made by Skype. Obviously even in a video call the first impression is always the one that stays, and therefore there are some care that the candidates must take into account.
Both situations have already existed: candidates who have made the effort to introduce themselves even if it’s only for a video call (shirt and tie for example) and there have already been situations where the candidates were on the street in a relaxed way talking about their professional experience while they walked through the city. And these kinds of postures don’t mean that they are right or wrong, they simply show me that there are a number of ways for candidates to look at life and how they press for a simple interview.
I always advise, regardless of whether the interview is online or face-to-face so that the candidates use a more Business Casual look.