Any update on this?
Whilst it is still feature that would make things much easier for index users, I have found this and thought I’d suggest. I use https://www.fitnesssyncer.com and have it linked to a free fitbit account, which is then synced to Zwift via native integration. As far as I can tell it is stable but I have seen in other posts that some users have to reconnect it from time to time, worth a shout until Zwift pick up native Garmin integration.
Haven’t seen this mentioned yet but a DC Rainmaker post says this is finally in the works.