Yeah i have a relative who wanted to switch to linux, due to windows being dog-shite, but she want's to have netflix with offline download feature.
Anyway it's a right pain in the arse.
I ended up going with the Waydroid emulator and using netflix android app.
It needs wayland so sadly I had to betray XFCE.
You can get it to work on the plain lineageOS waydroid image ( without gapps) - I think either via aurora app store or just sideload the apk into waydroid directly.
There's a waydroid utilities/helper script that installs widevine into the vitrual machine.
I got it working on stock debian+KDE(5), I'm not so sure about other distros but I assume GNOME would work fine also.
I looks like the downloading for offline view works, i'm not 100% sure whatll happen with disk space. And I didn't check the resolution available.
She's not actually switched over from windows yet, but we did a quick proof of concept.
I'm not sure if the waydroid route is easier or not but it's an option, and if you're wayland already that's one less hurdle.
UI through the emulator is s bit annoying, but manageable and you might be stuck with the android bar at the bottom so no true fullscreen.