After “Hamilton” made an earwormy global phenomenon from the life story of American founding father Alexander Hamilton, no chapter of history can be declared too dour for spangly, heart-on-sleeve musical treatment — though the Winnipeg General Strike of 1919 is still a pretty unlikely candidate. The stage roots of “Stand!” go back further than Lin-Manuel Miranda’s Broadway smash: It’s been 15 years since it first hit Canadian stages under the title “Strike!,” and the eventual film adaptation has the air of a patient, resourceful labor of love, while also showing why the material wasn’t more immediately rushed before cameras. Earnest and plainly felt, this grafting of a cross-cultural romance onto the story of a critical turning point in Canadian workers’ rights doesn’t want for incident and emotional commitment, but Robert Adetuyi’s film does fall a little short on showmanship.