You should Magisk hide Netflix. Apparently some people are able to retain L1 (it should be impossible with unlocked bootloaders.. Oneplus will lose l1 status upon unlock..) I'll see about trying to keep l1 on oneplus 7 pro.So you don't lose hd/hdr on Netflix with root?
It's true that it's old version, not true not having full screen. I have a mod Netflix I found here in xda with hdr and dolby it is old version but it worksUnlocked bootloader = widevine L1, period.
You can download Netflix app that apparently circumvents this and still displays HD video, but not working here (plus it's old version without full screen anyway).