Luna is the cloud gaming service from Amazon. If you have Amazon Prime, you have a small selection of games to choose from. If you pay for membership, you have a larger selection. Nothing is installed on your computer to play the games- it all works through a browser. If you use an Amazon Firestick, there's a dedicated app for it. All of the hardware is on Amazon cloud servers  they run the game and deliver the video feed to your browser.  As you can imagine, there's a bit of latency involved normally. Amazon runs the game, sends the video to your PC, you see action on screen and hit a button on your keyboard, which sends the action back to the server to execute. It can work with a Bluetooth controller connected to your PC, but that adds a bit of extra latency as Bluetooth has its own delay. A Luna controller connects to the Luna service directly via your wifi network to remove some of that latency. It's not required at all to enjoy gaming, but some people like the extra responsiveness. If your father wants to play on a fire stick instead of a browser, the controller may be necessary. More on reddit.com

I also grab it from APKMirror, so I can’t help you with that. But maybe you didn’t know that Luna also works pretty well in sideloaded Chrome browser. And that’s what I use as a backup solution when the Luna app wants an update that is not available yet on APKMirror. Stable Chrome even shows up on the Android TV launcher. So if you set the Luna website as your start page, you just have to open Chrome to play. More on reddit.com

I figured it out. Just had to go to Amazon.com/luna and touch the 3 dots in chrome and touch install app. Didn’t realize it’s only a PWA. More on reddit.com

It's simply a shame that users must sideload the apk in their TV or whatever... Why do not they release it in Google store? This is the only things that is preventing me to buy the luna controller... More on reddit.com