I used to cycle in my gym static bikes, record my activity under "Bike Indoor"->"Free Ride" and input data form the gym bike in the Garmin Connect app after the activity.
With the last update (Garmin Descent Mk3 on v15.62) I was surprised to see that I was not able to record my activity anymore. The watch starts searching for a sensor, which I don't have, fails and does not start the activity.
Can you make a bike activity option with no sensor?