I have seen old kitchen cabinets with places to store potatoes and onions.
I store mine in the fridge sometimes together because I did not know better so I ask Google.
This article from Taste of Home concludes what you stated:
But they should actually be stored far away from one another. Why? Your onions produce and emit ethylene gas, which speeds up the ripening process and can cause nearby potatoes to rot and spoil more quickly.
https://www.tasteofhome.com/article/how-to-store-potatoes-and-onions/
That article also says:
You know that potatoes shouldn’t be kept in the refrigerator.
Everyone knows you can't teach an old dog new tricks so I am going to continue to store mine in the refrigerator. I am not sure whether I will separate them though ...