I don't even remember the last time I visited a page which had issues because I didn't have Flash installed. HTML5 seems to have covered it for things like Youtube.
Most Smart TVs, set top boxes, and things like the Roku or Chromecast all run Linux, and they have Netflix, so clearly Netflix is fully supported on Linux. For desktop distributions you'll usually have to do something yourself to get it installed.
As I recall, however, I think some of Netflix's 4K content is only available on Windows 10 via the Windows 10 "App" and requires certain Intel CPUs as well. Obviously that isn't available on Linux.