I currently use Onelap (free), Perfpro (one time payment), occasionally i sign up for Zwift too. Most of the paid subscriptions services have a free trial of at least a week, so you could do around 2 months of free workouts over the winter if you try them all out - Trainerroad, Rouvy, Zwift, Sufferfest, Tacx training, Bkool, etc.