Apple devices are sometimes very contrasting. On the one hand, they can offer something that no other product can offer, and on the other hand, they can be several years behind the industry.
Thus, only the new operating system macOS Big Sur has support for video with HDR. In particular, you can watch Netflix in 4K HDR only on the new operating system. But it turned out that just updating your Mac to Big Sur is not enough – you need a PC with a security chip T2. And this is only available in Mac computers, released not earlier than 2018, and you need to look at specific models.
To be more precise, T2 is available in the new iMac 2020, iMac Pro, Mac Pro, Mac mini, MacBook Air from 2018 onwards, and MacBook Pro units from the same period.
It is completely unclear why Apple linked the video content with the security chip, but most Mac users will end up without 4K HDR support. It should be noted that the requirement is on the Netflix website, but it is unlikely that this company has introduced it itself.