take a look at playon. I paid 69.99 for a lifetime (however long that is). if you have buffering issues it may not be for you but it works for me. I also have amazon prime and roku as well
Still only single user though right. I can't watch something in one room while someone watches in the other.
I believe that is true. However, your sling account gives you access to ESPN and HBO apps that you can run on other tvs. But for the most part you are right it's restricted to one screen at a time.
My current setup... Old office PC as a backend server with 6 TB storage for movies, episodes, music, etc. It also has 4 tv tuners so that it can act as a pvr/dvr backend. Amazon Fire TV running Kodi. I use Kodi as the tv tuner frontend. I have the Kodi skin set to launch various Android apps such as Netflix. SlingTV, though I will probably drop the service soon. I can just use someone else's Cox login and have access to all of the same networks through their respective Android apps. Bedroom TVs all have the same setup except they have Fire Sticks. I will be upgrading them to full Fire TVs because of the much better hardware.
