I think it works the other way in Bubble world. You can make one column, then there’s a checkbox for “allow more columns if page is wide” or something like that.
Create a second repeating group (RG2) that has a state that makes visible RG2 when desired width is achieved. In parallel, RG1 will have its own custom state that not be visible at whatever the breakpoint width is. Or is only visible under/over a certain width.