I use Garmin Edge 530 Cycling Computer and there were few occasions when I needed to download a course from Garmin Connect (running on iPhone XR) while on the road with an activity running on the Edge 530. Normally, when you send a course from the Garmin Connect app to Garmin Edge you need to do a sync for the course to download. The problem is that syncing doesn't seem to be possible while an activity is in progress (the sync just times out or gives "device busy" error message).
One option is to stop and save the activity, sync the device to download your course and then start a new activity. If your course/route is saved on Strava or Ride with GPS, you can also use Connect IQ apps to download from there (Connect IQ apps don't work when activity is running). An obvious issue is that you will end up with 2 separate activities, but this can be resolved later when you have access to a computer - download both activities from Garmin Connect as .fit files and them combine then using FIT File Tools website.
Another option is to use GRouteLoader IQ widget. This free tool can be downloaded via Garmin Connect IQ store. Just make sure you download a widget and not an app version. This is because a widget can run while activity is in progress, which is exactly what we need! To download a course from Garmin Connect:
- Make your course public and get the course ID number.
To get the ID number on your mobile device simply share the course to an email or some chat app and it will show your course URL with the ID number at the end. i.e.: https://connect.garmin.com/modern/course/31257203
- Open GRouteLoader IQ widget on your Garmin Edge device and navigate to Download > GC Course (by number)
- Enter the course number you got in step one and download the course to your Garmin Edge. Obviously, your device must have access to the Internet via Wi-Fi or a paired phone.
GRouteLoader IQ also has the ability to download routes from Ride with GPS and some other third-party service, but I never tested this.
Garmin Edge 530