Facebook’s News Feed does not respect Universal Links. This means you cant simply deep-link out. If you google Deep-link out of Facebook, the first page of results on google has no options that are not facebooks SDK related or Branch.io. I do not want to use a facebook SDK in my app nor do I want to use Branch as it is a paid api. Ideally, I would use no SDK. I failed to find a complete SDK less solution.
My desired results are to leave facebook from a comment link. If you have the app, deep-link with xyz content if you do not have the app go to the Playstore. If you are on a browser go to the Playstore website listing.
Firebase Dynamic Links
After looking around I found that Firebase Dynamic links work to deep-link into your app from Facebook. The tutorial is self-explanatory and easy to follow have a look here. You can get a free domain here to combine with the dynamic link to make it look shiny. With the free domain forward all request to the Playstore listing so web users get directed to the store. This will only happen when a web user clicks the link. A sloppy but effective tutorial for that can be found here.
If you would like some inspiration for what you can do with your shiny new deep-links you can have a look here. Happy Deep-linking out of facebook.