Yes. Facebook at some point filtered links to them from private messaging. I know this from personal experience. Not sure if they still do.
Also fairly common on Reddit and Discord for communities to ban discussions of them, or even falsely claim they're blanket illegal outright.
Why? An emulator isn't legally any different than a virtual machine.
Low-level emulators can be legally identical to a virtual machine, but often isn't. Most modern consoles can't be emulated that way, and most require you to dump a bootrom from your own console hardware, alongside game keys and other dubious digital paraphernalia.
Just like a PC, bare hardware without firmware or a boot OS is pretty useless. Same with emulators.
Most distribute a pretty wide range of stuff along with them.