Most of my long ride training (specialty phase?) occurs on the bike. In-season will do one long ride a week, one or two VO2 or threshold workouts a week, then z2 anything else I feel like doing (ex: commuting). Not using TR at all during this, other than the occasional train now for indoor VO2 sessions when the weather is bad.
Winter on the trainer is about keeping fitness and improving FTP and such. There’s not really any long-distance specificity to it. This year I’m doing the 8wk high volume polarized plan and enjoying that, though have subbed in a weekly 2.5h tempo ride to replace one of the shorter z2 rides to help keep my volume up.