welcome back in every sense of the word. As for spinnervals, I have no advice but I can suggest a couple of podcasts. Cadence Revolution is specifically geared to riding, while pod runner and podrunner intervals provide a variety of speeds tempos and workouts including stair steps, fast slow and steady rate intervals.
Congratulations on your remission but as you return to it, please remember that you have been and are still recovering from a pretty much huge health trauma and be a little patient with yourself.