If your Mac does not have the small Apple T2 chip, you will not be able to enjoy Netflix in 4K (and HDR) on your screen. And this, even if an update of macOS to the latest version, Big Sur, should theoretically allow it.
The mere presence of a panel with a 4K definition or higher is unfortunately not the only hardware prerequisite for the 3840 by 2160 pixels of films and series to be displayed. In any case, this is what a user help document relayed by the site 9to5Mac unveils today.
It seems that the processing and management capabilities of DRM (digital protections) of the T2 chip are required by the video on demand platform. The site The Verge leans, for its part, for use of the video decoder in HEVC format which is installed in the small T2 chip, twice as efficient as that of the T1 model, and which Netflix could use.
Clearly, to enjoy 4K on Netflix, your MacBook (whether Pro or Air) and your Mac Mini must be models released since 2018. The 2019 Mac Pro, iMac Pro and iMacs of 2020 are also eligible. In addition to updating your macOS, you will also need to update your Safari browser and only go through it to play 4K content. Other browsers limit you to 720p on Mac.