Please see the video. I have enable Android 10's gesture control as someone said that was the issue. My phone is US version. https://youtu.be/b8e5JwS2mwo I first encountered this issue with Version WW-17.1810.1910.63. I have flashed .68's OTA and it doesn't help. I can't really wipe my phone as my phone has 1 irreplacable authenticator.
Even i got stuck two days ago but, I quickly found pretty easy solution for it. All you need is a Mouse ( wireless or wired ) and a OTG cable. Follow the video down below and everything will be back to normal. I will highly recommend to Turn off double tap home key gesture to enable One Hand Mode in Advance settings until this bug is fully fixed.
This seems to be a way to soft-brick your phone. If you have gestures enabled, and try to enable one-hand mode for the first time, then you become trapped in the one-hand tutorial, with no way to exit. Rebooting does not help.
If you happened to have adb turned on you may try fiddling with that, otherwise there isn't much to do other that updating the phone in recovery. It is also not a good idea to grey out the screen in tutorial more and not have the grey out area act as exit, something to bear in mind for other system apps that might have tutorials.