I have three active Roku streaming devices. On two of them I've been able to add the Peacock channel with no problem. On the third, it's as if it lives in a alternate Roku dimension where Peacock doesn't even exist. It's not offered as a featured or popular app and it does not turn up in any searches. I have updated my device as much as I can to no avail.
The same is true for the AppleTV+ app. Two of my streaming devices have it with no problem. With the third, it doesn't even exist. What gives?
Is it old? Some older Rokus are no longer supported especially by more recent apps.
What @Strega said. Many of the latest channels are not supported on older devices. On exactly what model Roku devices are they not appearing? Please, the model number, not just the name. Roku has a bad habit of reusing device names on distinctly different devices.
AppleTV+ is not supported on the Roku 4 (4400) or anything older than a Roku 3 (4200).
Looks like anything slower than the 900MHz Broadcom CPU was left out of AppleTV and Peacock.
https://en.wikipedia.org/wiki/Roku has a list of Roku internals.
https://www.apple.com/apple-tv-app/devices/ lists supported AppleTV Rokus.
https://www.peacocktv.com/help/article/what-devices-and-platforms-are-supported-by-peacock lists Peacock supported devices.
For more detail about hardware and what devices are still supported by Roku, you can see the information on Roku's developer site here.