The Mountainous gand fondo plan has 2 kinds of outdoor workouts for weekends.
One day is pure endurance. For that I ride where ever I like as my pure enjoyment ride Over hill and dale, usually scenic, and far. I just make an effort to stay in zone 2 and 3 and chill. It’s all about time in the saddle rather than mileage. That said, if there’s a fun little pinch of a wee TT effort I can’t resist, I’ll add that in, but then chill to keep my overall IF in the right ballpark. If I do a group ride for this that pushes me hard, then I dial back my other weekend session to compensate.
The other kind of out door ride they prescribe is intervals. Usually a long warmup of about half an hour. An hour ish of intervals. Then 30-60+ minutes if extra volume before a cooldown. I use the warmup to ride somewhere sensible to do the intervals. The “where” depends entirely on what the intervals are. If they are cadence drills, I literally ride on my own street (semi rural, gentle rise one way but flattish, and low traffic plus big painted cycle lane and 5km long). Or I might cycle to one suburb over if it’s short power sprinty efforts, as there’s a loop that works very well with a Short sprinty climb and a long flat recovery. Longer MAP efforts I ride to the local business park. It’s dead on weekends in terms of traffic and is a 3km gentle steady climb with a longer flat to slight descent recovery. And gives me the ability to expand the loop if I need a longer climb or recovery. OR, sometimes there is a long FTP threshold effort, then I ride to the local hill ranges where there is a nice big 12km incline climb and ride up there for those efforts then do a huge recovery loop before rinse and repeat. The prescribed outdoor interval rides are nice and simple and easy to execute successfully outdoors.
With riding the indoor sessions outdoors… i have on occasion built these into my headunit or Training Peaks and tried to ride them mid week. However, the intervals are SO detailed, that you never get the same out of the workout compared to on the trainer. 9 hammers is the “simplest” but then you still have to remember the cadence variations, make sure you’re on a climb for the low cadence intervals. It’s a nightmare, then trying to execute something with that level of detail while outside dealing with traffic etc, it’s hard. So I train indoors during the week and/or commute by bike for extra volume. Sometimes I look at the intention of the indoor session and apply that principal to my commute, but rarely. Mostly I just ride like a hooligan chasing eBikes and get somet out of it… usually exhaustion