How do I turn off the authentication process where AppleTV sends me a 6 digit code? When setting up AppleTV on Roku, I need t login to AppleTV, but I never receive a 6 digit code to complete the process.

Two-factor authentication is an account property. It is not device dependent. If it has been active for more than two weeks, then it is permanent for that account, and can’t be turned off. It is a security feature, ensuring that the account can’t be used on new devices without the account holder’s knowledge.

Two-factor authentication for Apple ID - Apple Support

Get a verification code and sign in with two-factor authentication - Apple Support

You should be receiving the verification code on any of your Apple devices (iPhone, iPad, iPod Touch, Mac), or else as a text message on a third party phone.

If you didn’t receive any code, then you can generate a fresh code at any time on mentioned Apple devices.

If you didn’t receive any code, then you can often click “Didn’t receive code” on the device where you were trying to sign in, and then enter a phone number to have it send again.

Your trusted devices and trusted phone numbers can be managed from your Apple ID account page.