In Germany, supermarkets typically post product recalls right on the doors or over the shelves of the section that has the affected products. I guess if you bought something you might be less likely to go down that aisle again next time and come across the sign, but (barring a big empty space at the entrance) I think that’s the most reasonable place for them to be
They’re not super common. I don’t see one every single time I go grocery shopping, though I would say typically there are maybe one or two recalls posted somewhere in the store at a time. Most I’ve seen at once is four, maybe a year or so ago, but they also keep the signs up for a few weeks so they didn’t happen all at once.
They do always have either a picture of the product or at least the name prominently placed, so you can glance at it to see whether it’s about something you might have bought.