@rpanbwl-
I don't know a way of locking settings in general.
You can set a PIN that must be entered to add a channel or make a purchase via your account at https;//my.roku.com..
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.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X