If you are unable to use the device keyboard to enter any texts in the Kiosk mode, please check if you enabled Hide the navigation bar of the bottom screen or Full-Screen Mode.
If enabled either Hide the navigation bar of the bottom screen or Full-Screen Mode, the keyboard will be hidden and you can set the time interval between 5~300 seconds.
After that, if you need to type on any apps (e.g. Chrome), please TAP on the search bar and SWIPE UP the bottom space and the on-screen keyboard will show up.
Note: please set a longer interval (e.g. 60s or above) in order to avoid the keyboard disappear.
Or if you don't need to hide the navigation bar and set it as Full-screen mode, you can turn them off, and the device keyboard will have no time restriction and you can type as you would on a regular device.