Hi there.

I had a problem recently with an updated version of VLC on Amazon fire TV -- was really bad compared with previous version -- especially if you like / use subtitles as the feature to load the subtitle from an external file when playing your own media has GONE !!!! (Android version 2.1.1)

I've long complained about not being able to restore previous versions of Android apps after a hideous update - a lot of app updates seem to be WORSE than the earlier versions -- VLC is a good example of this -- note the PC version is still EXCELLENT !!!

Anyway two ways now

1) store / keep the old apk file on your computer and then with a cli between computer and the target device you can install the old version directly via the CLI.

2) to install from Phone to Amazon fire stick / TV directly follow this guide

How to Sideload Android Apps onto Your Amazon Fire TV and Fire TV Stick

I managed to re-install prev version of VLC on to my Fire TV by uninstalling the version on the Fire TV and then following the guide.

BTW for a LAN / Home use it's a lot easier using VLC (on the fire stick - you don't have to do anything with VLC on your computer - you don't even have to start it or even install it) to play your multi media - it will browse your LAN etc. Saves setting up things like PLEX which while fine are a bit overkill and PLEX transcodes things like HEVC H265 codecs which can load your server and cause stuttering playback or even freezes if a few people are watching the movies -- VLC plays these codecs natively.

Of course there are advantages in using a media server - especially if you have several different remote TV's etc but if you primarily just want to watch your own media on a remote TV this is the easiest way to do it. You can use several TV's but then each one will need their own firestick which is why for several TV's a medfia server is the best way though.