remove sidebar from ipad

You need to explore multitasking - as you have a slide-over Safari view enabled. Key to accessing and controlling multi-tasking is the small “three-dot” button that is found at the top-centre edge of the screen.

More information about using multi-tasking can be found in this support page:

Use multitasking on your iPad - Apple Support

The iPad User Guide is also a rich source of information about using iPad and its many features. The Guide is available both online using a web browser (such as Safari), or as an Apple Books download:

iPad User Guide - Apple Support

https://books.apple.com/book/id1567104892

What browser are you using? It looks like the setting is ‘open new tabs in new page’ or something to that effect.

If Safari, I do have a setting (settings, safari) to request desktop site. If that’s turned off you could try to turn that on and see if you get a more desktop response than a mobile site response

In what app?

Can you post a screen cap?