I live in a rural community. Facebook has more or less replaced the web here.
Businesses post their hours, specials, and information on Facebook. Some of them don't have websites. The rec centre has a hard time keeping their website up to date, but the Facebook group is always accurate. Newspapers have closed down, so a Facebook group keeps people apprised of what's going on (it seems to be pretty accurate, since everyone in town is part of it, people involved in events chime in). Kids and adults sports groups advertise and tell their members what's going on via Facebook groups.
It's a shitty medium, since the Facebook algorithm mixes trash advertisements with town-specific events, but it seems to suffice for the town's needs.
I suspect it isn't just my town. The network effect is strong, so I suspect there are niche communities where Facebook is verging on ubiquitous.