I am NOT running nor planning to install iPadOS 15 any time soon!
As far as I am concerned, so far, iPadOS 15 is a hot steaming mess, right now, and maybe throughout the year!
I have not upgraded three full iOS/iPadOS versions on any of my devices, in thr past, prior to iPadOS 14, last year.
The ONLY reasons I did so was better external drive integration, improved multitasking and more integrated support for the Pencil which I purchased immediately after upgrading to iPadOS 14.
For the past 4 years prior, I had been using the Adonit Pixel stylus, which I will still use on ocassions.
I have NO problems totally sitting out an entire iPadOS version for a year, IF I think an iOS/iPadOS version is complete garbage and just changes for changes sake.
Search online for Home screen images of iPadOS 15.
Also, you'll see this issue in iPadOS YouTube videos.
You'll see the larger side margins on the Home screen.