Unable to disable multitasking on iPad

What is wrong with the multitasking?

You can disable most multitasking features by going to Settings ➜ Multitasking & Gestures and selecting the "Full Screen Apps" option instead of "Windowed Apps" or "Stage Manager".

Otherwise if you explain what issues you are having, someone may be able to help you reduce or work around the multitasking options.

For iPadOS 26, you have a configuration choice to use Full Screen Apps only, use Windowed Apps, or Stage Manager mode as you prefer:

Settings > Multitasking & Gestures - select your preferred multitasking mode