Moving waves on Spain’s film-TV scene when it launched in early May, Beta Fiction Spain has unveiled its first project as a producer, “Dolores,” a portrait of Spain’s Dolores Ibarruri, a worldwide icon of the workers’ movement and struggle against fascism.

The feature film is inspired by “Pasionaria. La vida inesperada de Dolores Ibárruri,” a question-posing non-fiction book by Spanish historian Diego Díaz Alonso published in 2020...