I want to watch hbomax on my other devices like xfinity flex
How do I let my Xfinity stream box use my hbomax subscription?
Apple TV (4th generation)
If you subscribed to HBO Max with payments through Apple, then that subscription is valid for Apple devices.
If you subscribed to HBO Max with payments to HBO Max directly, then sign in on any device on any platform with your HBO Max account.
To switch how you subscribe, you would need to cancel one and start a new subscription with the other.