Each channel/app on a Roku is a created by some content creator/owner or some other contractor/company that has an agreement with the content creator. Once the app is running, the developer has broad control over how the UI works. Anything that gets you linked to your account will work, and some channels don't require accounts at all due to differences in their business models.
I don't recall any QR when I connected Prime, but I assume it's just equivalent to giving you a code plus a URL to go to. That, and logging in with an account are just two ways to connect your player device to some account. At least one app I used, gave the option of doing it more than one way, because it really doesn't matter to them. ie: entering an account and password may take more typing and may require more from your memory (especially if you follow the common security advice of using different passwords for all accounts) but it doesn't require you to use a second device.
@Alan6098, I agree with @Strega . Plus, so many people seem incapable of typing in a URL without ending up at some scam site. The QR code hopefully makes it idiot proof (if there is such a thing).
Clarifying .... This only happens when adding channels. I am still curious why the process of adding channels is different sometime. For example 1) When I added Vudu and Peacock I was asked to login or creating a new account. I logged in, and the respective channel was added to my Roku. 2) When I added PBS and Amazon Prime, I was given a URL and a numeric code; and instructed to go to the URL and add the number that was on the screen - I followed the instruction, and the respective channel was added to my Roku. So I am still curious why the process of adding channels PBS and Amazon is different from adding Vudu and Peacock? All channels appear on my home screen as they should. When I select any channel I am taken to the home screen of the respective channel where I can browse and select content that I am interested in viewing on my TV - this too works as it should, so I am happy except not knowing why when adding channels the "process" is not same for all channels. BTW the QR code I mentioned is an option to typing in the number at the URL - I could read the QR code with my phone if I wanted to. I chose to type in the number.
Each channel/app on a Roku is a created by some content creator/owner or some other contractor/company that has an agreement with the content creator. Once the app is running, the developer has broad control over how the UI works. Anything that gets you linked to your account will work, and some channels don't require accounts at all due to differences in their business models.
@StregaMakes sense. Thanks 😀