iPad OS 15.5 home screen icons per row

Switching between Portrait and Landscape makes no difference other than switching columns vs. rows…

• With Widgets - Portrait (6 rows x 4 columns) to Landscape (4 rows x 6 columns) - 24 icon array
• Without Widgets - Portrait (6 rows x 5 columns) to Landscape (5 rows x 6 columns) - 20 icon array

iPad models with smaller screens differ in having a smaller grid array. While these models may display fewer rows/columns - rotation between Portrait and Landscape orientation should not change the total viewable icons on each Home Screen.

There are clear differences between iPadOS14 (and earlier) and iPadOS15. iPadOS14 lacked the ability to add Widgets to Home Screens. Instead, the Landscape Today View could be pinned - compressing the icon first Home Screen array. This view was not available in Portrait.

As you may have discovered, update to iPadOS15 introduced the ability to add Widgets to your Home Screens - some being added to your first Home Screen, by default, during the initial update to iPadOS 15.x.

Widgets placed on a Home Screen now individually occupy one or more elements of a fixed 4x6 icon grid array. Home Screens without Widgets retain the familiar 5x6 icon grid. Other than placement of Widgets, App or App folders within the fixed array grids, you cannot alter the layout.

The Today View being pinned to the first Home Screen was feature of iPadOS14. This feature was deprecated with introduction of iPadOS15 - being replaced with the ability to add Widgets to any Home Screen.