At Goldman Sachs Group Inc. and other US banks, staffers know that their bosses want them back in the office. Yet many of their colleagues at European firms are working about half the time from home. Their employers say that flexibility is a competitive advantage.  Every one of 12 top European banks surveyed by Bloomberg is continuing to allow employees to work remotely for part of the week. UBS Group AG even sees its embrace of hybrid working as a chance to hire talented staff from US competitors, according to a person familiar with the matter.