Get an A/V receiver, a computer monitor or dumb TV, and speakers. Then you can get a Roku streaming player and it cannot show you anything when you do not have its input selected on the receiver.

Even an inexpensive pair of bookshelf speakers placed on either side of the TV will sound better than built-in TV speakers. Add a center speaker and a subwoofer drastically improved sound.

Non-4k AV receivers are dirt cheap used.