Todoist, Things, TickTick, Habitica, Focalboard, OmniFocus, Wekan, Org mode, momentum.earth, Quire, Remember The Milk, sleek, Kana Reminder, GTDNext, IQTELL, Zendone, Vitalist, d:DONE, Mind On Track, Tudumo, Reddynote, Check Off, Managly, YouTasks, The Now Organizer, GTD Simple, ThunderTask, Wunderkit, B-liner, Happierco, Anxiety are some alternatives to Nirvana.