Browser would be simplest. Even though I prefer Linux and do run it, Windows might be better in your case with it having the DRM support and apps to run those services at higher resolution and HDR that sticking with browser might not allow.
For my case I picked up a cheap MiniPC and install Fedora on it to use instead of the TV interface.
People do pick up Pixel phones to install GrapheneOS on. How many people pick up Apple phones/tablets and are able to install another OS on it and have it as functional as GrapheneOS?
Same with smartwatches which from the Android side can be used offline with apps like Gadgetbridge to retrieve data without giving your watch internet access and not using the official apps.
Apple is very account and OS centric wanting to funnel everything through them. Exception has been MacOS devices which has had better luck with stuff like Asahi Linux.
My living room set up has been TV not connected to internet and hooking up a minipc running Fedora. Could run Windows if DRM content from streaming services is important to you.
Maybe snapmaker u1? I think their firmware is open source and if it goes the direction of bambu people are already able to run custom firmware, and printer functions fine completely offline.