Downloading a track offline from my Fenix 6X

I don't think it is possible. Without using the cloud storage, you can only sync waypoints and courses.

It is possible to download activities from the Fenix 6 via a USB cable to a laptop, and via USB OTG to an Android phone (I am not sure though, I have not done that for years), and the app IPBike can load FIT format (activities) and show them (as routes).

If your phone has a very good GPS (so that it makes good tracks without assisted GPS) it may be able to co-record your activities with an app, which is not a great option as it can consume a lot of battery power.

The Garmin Explore App should work offline, so you should be able to sync your track to your phone via Bluetooth 

Can you tell how you do that? I must be missing something!

I have never used it in a real offline scenario tbh, but the Garmin Explore App can for sure sync with your watch when your phone has no network. By syncing you will transfer all your activities, waypoint and courses to your phone. From the app you can then export them in gpx format if you want to use them in another app.

Or am I misunderstanding the question? 

Thanks for getting back on this!

I had a look at this Garmin Support Center article and I have a hard time interpreting it, but maybe the Fenix has to be connected to the phone via BLE during the recording of the activity, and/or the activity has to flagged as 'not yet synced'. I'm going to test that.

Update: Awesome, it works! As long as the device is known/registered in the Explore app before you start an activity, it will sync the new activities offline. And you don't have to have the phone with you. 

Many thanks #Matthias# for sharing this!

but maybe the Fenix has to be connected to the phone via BLE during the recording of the activity

NO

You're right, it does not have to be connected to the phone!