No laptop or Wifi transfer GPX to 66i using Fenix/instinct/Marq ? Possible "extreme" solution ??

Currently you cannot transfer a GPX file directly from an iPhone to a 66 series GPS and I wondered if the following "extreme" workaround is possible/works

I don't currently have any of these devices (because of this major shortcoming) and have pieced this info together from on-line

1. GPSMAP66i/st/s
2. Garmin Instinct/Fenix5or6/Marq watch
3. Garmin Explore App
4. Garmin Connect App
5. iPhone in Airplane mode but bluetooth on

Test Instructions
1. Make sure the 66 and watch are paired with the iPhone, work with BOTH apps normally
2. Have an email with a GPX file attached or another app that can export GPX from
3. After everything is setup make sure the iPhone is in Airplane mode and Bluetooth on
4. Use the share sheet to import the GPX from the email/app into Garmin Connect
5. Goto Training>Courses and send the imported GPX to the Instinct/Fenix/Mart
6. Switch to the Explore app and sync the watch with it
7. Hopefully the course is now in the Explore app too. I believe it might show it under Track Manager ?
8. Can you now sync the course with the 66 ?
9. Did it work ? have you gone from a GPX on iPhone to a route on the 66 without using an internet connection and or a laptop ?

Thanks very much in advance !