In 2019, a group of fintechs with names like Dave and Varo stood poised to disrupt the U.S. banking giants. Built around a digital-first strategy that didn’t require branches and tellers, the upstarts looked like the wave of the future—until they stumbled badly in the face of a shifting economic and regulatory climate. One of these fintechs, or neobanks if you prefer, found a way to defy this broader trend: Today, the San Francisco–based startup Upgrade is sitting pretty with a diversified line of business ...