Ive sold and bought on FB. Best to sell on local groups, there are a couple good ones in my area, I also like the Canada only groups with CDN prices only, no nasty conversion!
Another route is to join a few groups, get a decent rep then start your own page where you can direct all your sellers to check out your static stock
If you are a seller at cons it’s a good place to presell your wares before a show
A drawback to FB is the clique-y aspect of some groups, favourtism and whatnot, but that exists here at times as well.
Also for people complaining about notifications, you can set that sh** to whatever rocks your boat. No notifications if you want