Diversity opponents say the practice leads to discrimination and promotes left-wing ideology, while supporters say it helps level the playing field for women and people of colour.

On the opening night of Web Summit, one of the world’s largest tech conferences, the final speaker, though high profile, was not someone associated with the tech industry. Quite the opposite. In a surprise appearance at the annual event hosted in Lisbon, Portugal, Ukrainian first lady Olena Zelenska told a rapt audience about how Russian...