LONDON/HONG KONG—Bitcoin hovered on Thursday below its all-time high struck a day earlier after the launch of the first U.S. bitcoin futures exchange-traded fund, though J.P. Morgan analysts voiced doubt over its impact on cryptocurrency investment flows. The world’s largest cryptocurrency traded flat at $66,032, erasing slim losses made in Asian trading hours, after hitting a record $67,016 on Wednesday. Bitcoin’s rally to its latest peak—six-month after its previous top of $64,895—was fuelled by the launch of the ProShares Bitcoin Strategy ETF. Investors have bet this will open a path to greater investment from both retail and institutional investors. Yet some analysts at major banks voiced doubt over how long-lasting the boost to bitcoin prices from the ProShares ETF, which trades under the ticker BITO, would be. “Will the launch of BITO by itself bring significantly more fresh capital into bitcoin? We doubt it given the multitude of investment choices …