Thought I'd give this another go with a recent TVNZ Apk update. I'd heard a number of apps work better on FireTV if you use the AndroidTV version of the play services.
Using ADB I needed to install the following support services
You can get these from https://www.apkmirror.com/
For the TVNZ APK I still need to use the tweaked version from Matt Huisman's site that disables the HDMI check. He's got the latest 2.9.2 release.
adb connect firetv
adb install com.google.android.gms_11.5.18_*.apk
adb install com.android.vending_8.0.28.R-xhdpi_8_PR_163004339-80802868_minA*
adb install com.google.android.gsf_5.1-1743759-22_min*
adb install 2.9.2-mattrix.apk
With this combination I was able to login, browse and view content providing I had a bluetooth keyboard and mouse. This is somewhat less than optimal and won't meet the WAF level for general family use.
My main issue is the errors appearing in the firetv logs due to the Google Play libraries, which appears to be slowing down the FireTV.
Has anyone here had more luck with trying to get this working on their FireTV.