Their phone app from a few year ago definitely had a free-ride option. But, I use Trainerroad all the time. It's the best for what I want, which is basically it's training plans and variety of workouts. I don't want Zwift nonsense, I just want a power curve to follow and some useful numbers.
If you have a Wahoo, their app does that. Tacx Neos let you just jump on and they'll up resistance to some level.
I've also programmed Computrainers to do this but I presume it unlikely you're talking about a CT unit.
Trainerroad - can you run it in demo mode or something without subscribing?