When my wife wanted to start using Zwift I thought sure, no worries, I’ll just add another user and we can swap between as necessary. I wish! I run the Zwift app on Apple TV and have the Companion app on my phone to control. I had the basic Apple TV remote, so had already noted that there was a lack of ability to control the Zwift app using this as there was no response to the arrow buttons, but I could still do what I wanted. On trying to set up a second user without the ability to use the arrow keys I could not select Change User. I thought I’d just try having her use the Zwift app on her phone and mirror that, but in doing this the app would not recognize the Wahoo trainer. I tried everything to resolve this issue (e.g. turning off my phone so it could not interfere) but no good. Eventually I loaded the Apple TV remote app onto my phone after watching a YouTube video and seeing this was an option - up till then I didn’t know there were more advanced Siri remote and app was available. This allowed me to select Change User and then add my wifes account. With this we are now good to go, able to move between accounts as necessary. So the key is that you really need to have either the Siri remote or the remote app on your phone. We do experience the problem that others mention in that it is a bit of a lucky dip exactly where the cursor goes when you are scrolling, but you eventually get where you need.
Glad to hear you were able to get it all set up @Paul_Connor1. Another thing for people with multiple riders/runners in the house is that from my understanding the Zwift AppleTV app will only store 2 users info, if you have 3 then you will have to manually add the 3rd one each time, you can’t just switch over to them.