That's a fine solution if I'm only curious about whether one place is open. I want to know what options I have and I may want to do it late at night or in the morning rather than call twenty places during a busy period.

This is a serious problem. Maybe an opportunity for a SaaS solution with a monthly fee.

Or stores could just not require you to log in to see their posts. Many already set it up that way, I don't know why some don't.

Calling them is literally how people did it for decades. I think you can make due.