CRA's unusable two-factor authentication
https://www.canada.ca/en/revenue-agency ... vices.html
It does not allow opting out.
It does not allow you to change your phone number once you give them one.
It does not allow VOIP land lines.
It does not allow international phone numbers.
It does not allow e-mail.
So the only way to get tax information now is to go in person to a Tax Services Office. Oh, but those are closed due to Covid. So there's no way to get or submit tax documents now.
Good news. They now allow multiple numbers, changing your number online, and calling VOIP lines. Still no e-mail, international numbers, or opting out, but this is now more usable.