Kevin Bradley aka nitoTV, has just released the initial version of his eponymous tool, nitoTV for tvOS. NitoTV is a package manager and can install and remove packages on your Apple TV 4 or 4K, just like Cydia does on jailbroken iOS.
This release will run on tvOS 9.x-10.1 and tvOS 10.2.2. nitoTV requires a jailbroken firmware, at this time Apple is still singing tvOS 10.2.2 so you can downgrade to this version. If you are on tvOS 9 you can use the Pangu Jailbreak tool or the LiberTV for tvOS 10.x, and greeng0blin for tvOS 10.2.2.
nitoTV says Support for jailbroken tvOS 11 will come at a later date. You can download the nitoTV tool directly from here.