Apps on 6th gen ipad won’t stay open

What is the rated, internal data storage space/capacity of your iPad model and how much of this free, internal data storage capacity is left inside of your iPad model?

All of that additional info can, also, be found in the Settings app, General settings panel, About.

Your iPad needs sufficient free internal data storage space. At the very least, between 4-6 GBs , or greater, internal, free data storage space.

After ANY iOS/iPadOS upgrade/update, you should ALWAYS perform a simple hard reset/forced restart of your Apple mobile device.

Also, For iPad models with a Home button, do a simple hard reset/forced restart of your iPad by holding down both the Home and sleep/wake/power button simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

Best of Luck to You!

Make sure all third party apps are updated through the App Store app.

Also, Apple just issued a small security update, try running and installing that security update into your iPad, as well.

Most times, Apple includes other quick fixes within a security uodate, other that just the security fixes, alone.

Best of Luck to You!