I don't believe it's directly compatible but you can probably still use it with the cycling classes. You apparently need equipment that is "GymKit" compatible for Fitness+ to control the equipment. I've not looked at the details for that yet. I've been using my Wahoo KICKRsnap. The workout data onscreen comes from your Apple Watch. It's not clear to me what you might gain with a GymKit indoor cycle. Perhaps it will control resistance and maybe measure speed and cadence but I've not seen info on that yet.
With the Wahoo snap I run the Wahoo fitness app on my phone which collects speed, cadence and heart rate from my Wahoo TICKR. On an iPad I run Fitness+ to follow the indoor cycling video. On screen it shows heart rate from my watch so that's what is used to show the Burn Bar for comparison purposes. The video does say want cadence you might want to be at and to add or reduce resistance so you could do that manually on any indoor cycling setup.