Deeplinking to someones facebook profile from your mobile app is harder than it should be. I think at some point the syntax changed, so I spent quite a while trying to sort it out, now you don't need to!
Stackoverflow is full of I guess old articles saying the facebook uri is like this:
fb://profile/username or fb://page/username.
But it doesn't work, just loads the facebook app to the default your profile view.
I guess as of a certain version it is required to load into a special child view or something, anyway, this is the code that works.
Was super straight forward on iOS
fb://profile?id=username
This was tested by me using Nativescript 6.5 Typescript, however this isn't Nativescript specific.