It is not possible to use autofill function from iPhone to enter password while logging on to Zwift on AppleTV. I have tested on two different AppleTV, with both generations of remotes.
Hi Tom. I encountered this issue earlier in October. In my personal opinion, this bug is one of the most annoying things I have ever dealt with. Anyone who uses a password manager is likely using a password like a#4hfksur%jFJsnfkw$$1^da (not a real password). Imagine having to type that using an AppleTV remote. I had to change my password to something insecure so I could login using the remote.