My phone woke up in my pocket, I don't know how long, and now I have this big margin in Gboard.
All other functionalities look ok. Tried rebooting, but no luck there. The phone is a Poco X5 Pro.
How can I fix my keyboard?
This looks like a new keyboard resizing feature introduced since Gboard 13.2.05.x.
According to 9to5Google - Gboard rolling out an easier way to ‘Resize’ and customize your keyboard,
“Resize” appears as another toolbar/tray option. Tapping takes you to a UI that starts by letting you make Gboard taller or shorter, [...]
[...]
If you’re not taking up all the available space, you can move the keyboard. If you drag it up, you’ll see empty space beneath the last row/spacebar. [...]
(Emphasis added)