BRUSSELS—A storm in a beer glass is raging in Belgium. Traditional brewers are sour about “beer creators”—Internet-savvy startups who create recipes then employ other Belgian brewers to make the final product.

“They don’t get their hands dirty, they don’t have pain in their backs, the only thing those guys do in a workday is sit in front of a computer,” said Yvan de Baets, a co-founder of Brussels’ Brasserie de la Senne, a brewery in the Belgian capital. “They make a lot of noise on social media.”

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