I recently purchased a Sharp Aquos TV with the Androidtv OS. The TV works great, with a couple of configuration issues, but not related to the OS. The 4K stream from Netflix is freaking awesome! I am looking for a means by which to load apps that are not available through the app-store, specifically Skype and Playon Client. Any help or guides that I can get or be pointed to would be greatly appreciated.
Try sideloading with a USB drive and ES file explorer. I don't know how the Sharp TVs use removable storage but your app hunt will be a long one. You could also find apps through the web play store interface which has some apps not shown in the regular play store.