On iOS 26, if in "Single App Mode", the device gets stuck on the lock screen.
Devices are configured in SAM (kiosk mode), without a PIN requirement. Since updating to iPadOS 26, every single device that locks (goes to sleep) becomes completely unresponsive at the lock screen. Touch input does not work.
The only way to regain access is to reboot the device, which will boot to the SAM app, but then lock again if it goes to sleep.
Related discussion in the public forums.