What do you mean 'from the right side' ? One of the features of iOS 13, or perhaps iPad OS, is a new mode for text input – you can turn the full-width keyboard into a smaller, under half width and floating, keyboard with a gesture. This obscures less of your content and is better for one handed typing.
It was highlighted in the keynote on Tuesday. I don’t have iOS 13 so can’t check it myself, but it’s shown here under 'Keyboard'.
If it’s this you are seeing it may be by design. Maybe it’s the new default, or maybe something the user can specify in the settings or that it remembers from another app. As it’s under user control it may be something that apps cannot control, they just have to deal properly with the two modes.