Filter for Popular FB Group Posts

I've been using reddit to help me get a better understand of my audience. Basically I create a new account subscribe to all the subreddits that pertain to my niche and then they send me a daily email with the top threads. Super convenient for me. Now I'm trying to do the same thing with Facebook but it seems like A) they don't email me and B) there is not a way to sort my feed by posts with the most engagements. Does anyone have a trick or know of a tool that can help me isolate the most popular FB group posts across multiple groups?

No direct way. FB sends a random notification for some popular group posts but that's about it.
It may be possible doing it with a custom bot. Talk to a coder.