Bike uses custom characteristics.

• Device name: "CHRONO" + a number (mine shows as "CHRONO 12")
• Telemetry characteristic: A026E01D-0A7D-4AB3-97FA-F1500F9FEB8B (under service A026EE07-0A7D-4AB3-97FA-F1500F9FEB8B)
• Streams a 19-byte packet about once per second as soon as notifications are enabled, no handshake needed
• Packet starts with a fixed 3-byte header: 0x53 0x59 0x16
• Power: bytes 17-18, uint16 little-endian, watts, no scaling
• Cadence: bytes 8-9, uint16 little-endian ÷ 10, RPM
• Also available if useful: speed at bytes 6-7 ÷ 100 (km/h), distance at bytes 10-12, calories at bytes 13-14, heart rate at byte 5, elapsed time at bytes 3-4

User shared the following example implementation:

https://github.com/TrackMyIndoorWorkout/TrackMyIndoorWorkout/blob/develop/lib/devices/device_descriptors/precor_spinner_chrono_power.dart

I tried to follow the custom implementations used for other similar bikes (Echelon)