Disclaimer: Boring Video.
For some Reason Android 8.0 with facebook messenger will autoupdate on it’s own. I thought google had locked down on apps that try to auto-update on their own, but I guess some apps can do that now AGAIN.
This video shows how to disable the auto-update installer for facebook messenger version: 18.104.22.168.109 on android 8.0 for my LG g6. Hopefully you aren’t as annoyed as auto-updaters as I am.