There’s !todayilearned@lemmy.ml

I do, but I think it only shows communities from other instances that your instance already “knows” about.

people in your server having subscribed to one

This seems likely, because I also read that you can’t go directly via link through your own instance, unless your instance already “knows” about the community.

Yeah, but that one only shows local communities AFAIK. I also find it a bit of a hassle if I see a recommendation for a community on another instance, and want to subscribe.