Sorry, but that's just the way it works. There is no "main" Roku. Any channel/app added or removed from one Roku device will get added or removed from all Roku devices linked to the same Roku account. Plenty of complaints have been filed over the years, but Roku seems to have no interest in changing the way it works. If you want different channels/apps on different devices you must link them to separate Roku accounts. The downside to having multiple Roku accounts is that any subscription/purchase paid through Roku will only be available on the device(s) linked to that account. That's one reason why it's usually best to subscribe directly with the various provider, not through Roku.
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