This is the timespan for public-root after the Release of a new TV-Series -> 1 Month to 2 Years. It differs. J-Series-Root for instance took very long.
For USB Recording for your TV Model, as far as i know, that is disabled by Software and you can unlock it via Service Menu. To display the Service Menu you might need another Remote.
there was a sale in our region, so i get the UHD TV MU6479 for € 879, i couldnt resist and bought it.
I think when i discover the web interfaces and the samsung sdk, that there are some side loads are possible.
I try to inject in the app services and post when i discover some stuff.