@sambou-
Your channel choices are attached to your Roku account, and any Roku linked to that account gets all those channels. Add/remove on one, add/remove on all.
Had you linked your new Roku Ultra to a separate Roku account (i.e. to a different email address) the two would be separate, would be logged in separately, and could have separate channel lists. If you now want to split one or the other off the present account and into a new account, do a Factory Reset on it. A Factory Reset is initiated via Roku menu path Settings > System > Advanced system settings .
Following a Factory Reset you'll be setting the Roku up all over again from scratch, as though it were new right out of the box, including setting up your network connection and linking it to your existing or new Roku account. If linking to an existing Roku account, all your channel apps currently attached to that account will automatically be installed -- some of the ones requiring a login may require you to login anew.
Note that the subscriptions for any premium channels you subscribed to THROUGH ROKU will remain on the original Roku account and not carry over to the new Roku account.
Since it sounds like you'd like the majority of your streaming channels to reside on the Ultra, it would be less work to leave the Ultra alone and do the Factory Reset on the TV, adding only what few channels you want (if any) to the TV.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X
