Why you can not install it on OSMC?
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1st how do you know that “we” (whom I assume you mean with “you”) can not install this on OSMC.
I actually believe I could install ngnix on my OSMC if I see the need.
But actually quickly reading thru the page you posted I believe you could do this directly with Kodi without ngnix.
Unfortunately I don’t have a windows machine to test it.
you can but you have to know what your doing with a linux system 