For Amazon FireTV you can update it manually...Just install the right apk of VLC.
First I used the app Downloader to get essential apk files on the FireTV. Before that you must allow installation from unknown sources in the settings of the FireTV.
For frequent transfers of apk files I can recommend total commander and the LAN Plugin. No root required.
On the Fire Tablet I installed the Google Play Store...with an instruction I found with Google.
BR, Florian