Depends on where you are, I'm sure. Here in Norway, for example, the XBox Series X is still extremely limited. I can't buy it online at retail price, but I could apparently travel 20km from central Oslo to the suburb where one store lists it in stock for in-person purchase only.
Took me months to get my hands on a Series X, maybe things have improved but only recently.
Which ones? The Series S, or X?
Both, granted we have 3 Wal-Mart's within 8mi and we visit one of them a few times a week.
My guess is that at launch and many months after launch most of the stock was being distributed in higher quantities in the US. It was pretty hard to find an Xbox here in Spain, both were selling all the units they could make. Seems the stock is improving now.