Hi. I use Strava as my hub and sync Peloton there and it works great. I don't believe Strava syncs directly with mapmyfitness but I think you can do it by syncing to Apple Health and from there to mapmyfitness. Not ideal but may work for you if you're set on mapmyfitness. May also be possible via Google - not sure though.
support.mapmyfitness.com
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Apple Health
In order to connect the Apple Health and Activity apps to MapMy, please follow the instructions below. Open the MapMy app and select the Menu ("...") at the bottom right. Scroll all the w...
