This fervently supportive documentary about the iconic lesbian magazine Curve and its founder-publisher Frances “Franco” Stevens is directed by Stevens’s wife, Jen Rainin, and it’s both energised and hindered by her preaching-to-the-choir approach. Stevens was a San Francisco woman who in the 1980s got married young, came out as lesbian, was shunned by her family and briefly became homeless. In 1990, she launched what was then called Deneuve magazine by maxing out a handful of brand new credit cards, betting everything at the horse races – and winning big.

It’s a staggering story, virtually the American dream in action, especially as Deneuve went from strength to strength, with celebrity interviews, national ads and rocketing circulation. Stevens had the courage and vision to put the word “lesbian” on the cover, and gay women responded passionately to her mission to bring them visibility.

In 1995, French movie star Catherine Deneuve sued the magazine for trademark infringement, after which it changed its name to Curve. Actually, Stevens has always denied that that it was named after Catherine Deneuve, and a brisker-minded documentary with more objective journalistic nous might have pressed her harder on this and other points, and tried interviewing Deneuve herself.

Stevens became disabled after an accident two years later, and the stress led her to sell the magazine to another publisher; she was forced to look on aghast from the sidelines as her creation (like all print publications) struggled in the digital age. But even more seriously, the new Curve removed the word “lesbian” from the front cover because it was perceived as exclusionary by younger generations of queer women. Stevens had campaigned so fiercely against the erasure of lesbianism. So how does she feel about that? This film never really tackles such difficult questions, but it’s a valuable portrait of a great risk-taker.

• Ahead of the Curve is released on 4 June in cinemas and on digital platforms.