LeCoach workouts reach your Garmin through Intervals.icu: LeCoach syncs your plan to Intervals.icu, and Intervals.icu pushes each workout to Garmin Connect, which sends it to your Edge or watch.
Setup (one time)
Connect Intervals.icu to LeCoach in Settings - Integrations.
On the Intervals.icu connections page, connect Garmin and enable 'Upload planned workouts' (and 'Download activities' so your rides flow back).
Your scheduled workouts now appear in Garmin Connect's calendar and on your device, as full structured workouts with step targets. On ride/run day, the day's workout is typically suggested automatically when you start the sport profile; you can also find it under Training → Workouts on the device.
Workout not on your Garmin?
Check the workout exists in your Intervals.icu calendar. If not, see sync troubleshooting.
Check 'Upload planned workouts' is enabled for Garmin on the connections page.
Sync your device with Garmin Connect (open the Garmin Connect app, or on an Edge: sync via WiFi/phone). Workouts usually appear on the device shortly after they're in Garmin Connect.
Garmin generally receives workouts for the coming days; workouts further in the future sync as the date approaches.
Running workouts show heart rate instead of pace?
That's an Intervals.icu target-priority setting. Set the priority to Power > Pace > HR — full explanation in Why do my workouts give HR targets instead of power or pace?
Which data flows back from Garmin?
Everything Garmin records — activities, HRV, resting HR, sleep and more — flows to Intervals.icu and then into LeCoach automatically. Note that Garmin-proprietary metrics such as Body Battery, stress score and Training Effect are not part of that stream, so LeCoach can't see those. LeCoach's own recovery score is the equivalent it works with.
Your FTP on Garmin vs LeCoach
Garmin's FTP estimate and LeCoach's FTP are maintained independently. LeCoach uses the FTP from your Sports Settings, which by default follows Intervals.icu. See FTP vs eFTP.