I completed my first Zwift virtual run today.
Garmin pushed update 8.10 to there Fenix 6 watch on the 23rd of March.
My first attempt at using the watch with Zwift after the update was unsuccessful. The watch would show ready to pair. The app would show the watch as being paired. But the app would never show any of the information it was receiving and the avatar would just stand there.
After some quick research, I discovered that the watch needed to also be updated using Garmin express. After the quick update, the watch paired with Zwift and I was literally off to the races.
I also used the Garmin HRM-Run chest strap, which seemed to work well with Zwift. I look forward to many more runs with Zwift. Hopefully this helps some other users out there.