Yes, I might be able to help. I changed my Onn set top box (which uses Android TV) fairly recently to use FLauncher (or Projectivity, I don’t remember which one I chose in the end), but it kept defaulting back to the default launcher. So I jacked it to change what the detail launcher was. After enabling some options ( developer options, USB debugging, verify apps over USB) on my Onn box, I plugged the box into my computer and then used the adb command line tool to change the default launcher (launcherx).

I imagine you could do the same to your Android TV. As long as it has a USB port.

Hope this helps.

ETA: Here are some more detailed instructions I took when I did this:

1. On the ONN tv box installer flauncher and/or projectivity launcher via the Google Play store

2. Make sure developer options is enabled on the ONN tv box (hit okay on Android TV OS build several times)

3. Look up IPv4 address on the ONN TV box under Settings > System > Status

4. Go to the new Developer Options menu item on ONN > settings > system, and make sure: a) Enable developer options is set to on b) USB debugging is set to on c) Verify apps over USB is set to on

5. Download adb platform tools on windows from here: https://developer.android.com/tools/releases/platform-tools8

6. Plug in usb cable between PC and ONN tv box

7. On the ONN tv box go to Settings > System > Developer Options and make sure Select USB Configuration is set to MTP (Media Transfer Protocol)

8. On Windows, open a command line as administrator and go to the adb path

9. In the command line window on windows type: a) adb start-server b) adb connect [ONN ip address] (Note: it might initially say “failed to authenticate to [ip]”, that’s okay, see the next step)

10. On the ONN tv box a pop-up window should appear asking to allow access from windows pc IP address, say OK

11. In the command line window on windows type: adb devices

12. You should see the device as active on the ip you stated and on port 5555

13. Next in the terminal window type the following to disable the default ONN tv default launcher and listener: adb shell pm disable-user --user 0 com.google.android.apps.tv.launcherx

14. Then in the terminal window type: adb shell pm disable-user --user 0 com.google.android.tungsten.setupwraith

15. On the ONN tv box click the home button. It should now either a) go to the additional launcher you installed or b) prompt you for the home app (if you installed multiple additional launchers) so select the one you want (e.g. FLauncher)

16. Now when you hit the home button on the ONN tv box it should always take you to the FLauncher launcher, not the default ONN launcher

Note: If you need to re-enable launcherx, you can use these commands in adb:

adb shell pm enable --user 0 com.google.android.apps.tv.launcherx

adb shell pm enable --user 0 com.google.android.tungsten.setupwraith

My adventures with doing this were based on this post on reddit.

Try Projectivy.