Netflix can run on a device not certified based on a modified phone app
Version 4.16 which is available from the Netflix help center will not work on some devices including the Mecool KM9 Pro running Android TV 9
I found and tested 3 different versions which work on a device not certified, all are based on Android standard apps made for phones and tablets
Go to Android TV App Launcher Builder and create an APK file for the Android TV Launcher and Home Screen, or download it from here, if you have sideloaded the app on a device running Android TV (not necessary if the device runs standard Android). Should the url not be available anymore visit my guide on how to create an Android App with Android Studio. This allows to pin a small Android TV app to the Home Screen, which when started will start another app (in this case Netflix for phone/tablet) and exit.
Patched App v4.16.3
Follow guide Netflix HD Patch APK. This guide shows how to use the tools necessary to create a patched version from stock v4.16.3. build 15172.
Streams in Full HD with HDR and Surround 5.1. The categories to choose the movie from are displayed in SD, and the stream will take a few seconds to recognize the network speed and switch from SD to HD, which is a feature built into the Netflix app to adjust to low network speeds.
Netflix will ask to update to a newer version on first run, select cancel and do not update
The user interface was built for phone and tablets, but can be somewhat navigated on a TV using the remote. However, it's easier to use with an air mouse (or conventional mouse). I found this G20BTS bluetooth air mouse which can fully replace your original bluetooth remote, with 2 restrictions. For one, it does not have a microphone so you cannot use voice to command your box, and the power button might not work depending on the box you are pairing it with. Order it from Alibaba, it's less than 10 USD.
If you use a wired connection you need to use my patch file. The original patch file does not fix an error in recognizing the box not being on a cell network and does not allow to stream over a wired connection.
This is the version pre-installed on the Mecool KM9 Pro device with Android TV 9. I have not verified whether the app is still available on the Android TV 10 build.
Netflix will ask to update to a newer version on first run, select cancel and do not update
The user interface was built for phone and tablets, but can be somewhat navigated on a TV using the remote. However, it's easier to use with an air mouse (or conventional mouse).
APKMirror App 6.26.1
Download v6.26.1 build 31696 from APKMirror. I would assume that this apk must have been modified, as every other apk released from Netflix would not run without modification.
Netflix will ask to update to a newer version on first run, select cancel and do not update
The user interface was built for phone and tablets, and cannot be navigated on a TV using the remote. You need to use with an air mouse (or conventional mouse).