Wouldn't creating a second user in chromium do what you want here? You could have a specific "social media" user.
Incidentally, Chromium is what I use for Facebook...and only Facebook, on this particular computer. And signing into Chromium with my Google account seems to me to be a big information leak.
https://superuser.com/questions/377186/how-do-i-start-chrome...
you do realize that facebook etc still track you, even if you're logged out, right?