Etiquette dictates that if the other side of the conversation is audible to others (e.g., speakerphone, or Zoom/FaceTime without earbuds) and the other participant(s) is not in the same place, it's inappropriate to conduct it in public. Especially if the venue is at least theoretically expected to be a place of quiet and/or relaxation. In practice, airport lounges are generally something else entirely, but I would still give speakerphone users a sideways glance.