If you have connected Intervals.icu to LeCoach and performed a Full Intervals.icu Sync then normally all your activities, workouts and wellness data should sync to LeCoach.
However, due to policy changes at Strava, activities with Strava as the source might not show up in LeCoach, or show with incomplete data ('Untitled Activity', no activity data). LeCoach will show a warning on affected activities, with a built-in fix wizard to guide you through the solution below.
The solution
On intervals.icu/settings/connections connect every single platform you actually record with (Garmin, Wahoo, Zwift, MyWhoosh etc.) and enable 'Download activities'. Don't worry about duplicates — Intervals.icu takes care of those.
Once connected, also press the 'Download old data' button for that platform to import old activities, wellness and workouts.
Go back to LeCoach and run a Full Intervals.icu Sync in Settings - Integrations.
According to Intervals.icu you can leave Strava enabled for 'Download activities', but if you never record with Strava as your primary source, consider turning it off.
Recording activities with the Strava app?
If you currently record your rides with the Strava app itself, we recommend switching to recording with, for example, a Garmin or Wahoo device or the Zwift/MyWhoosh app — those deliver complete data.
Last resort: import everything
If historic activities are still missing after the steps above, you can download your raw data archive from Strava and import it into Intervals.icu. Instructions are here. Afterwards, run a Full Intervals.icu Sync in LeCoach again.