It isn't paid codec anymore. But you're right, it is not available by default to all computers/manufacturers.
Except it still isn't free, Microsoft ain't paying the licensing fees for it the fact the left a "Convenient way" to get decoder license in M$ shop doesn't make it free.
Case and point the HEVC official extension off the windows store.
And while a lot of other applications DO license HEVC (OBS,Nvidia,AMD, etc...) on their players and encoders the OS by default doesn't , at least on the DECODER side, and funny thing is neither does unity unless you pay for the license yourself on a per machine basis as indicated in the on the unity documentation here
You must be registered to see the links
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Also let's not forget the fact that anyone that doesn't have an atleast 1000 nvidia series or an AMD 300 series gpu doesn't have the ability to decode it, intel started having igpu support since the skylake and alot of people still haven't upgraded over haswell.