Apparently Samsung has exclusive rights for the HBO Go smart TV app in the US. I could install the app on my TV by changing the location to Mexico, but I got an error message saying "HBO Go is only available in certain areas of Latin America. If you are located in Latin America and you are having trouble accessing HBO Go please contact your distributor. IP address: xxx.xxx.xxx.xxx (US)". So even with the app installed, it won't work because their server identifies the location through the IP address. The only way is to have your TV connected through a VPN (illegal I assume) or with a compatible device (Chromecast, Ruku, etc) or via some stream apps (Amazon prime video, Hulu, etc).
