Always like on the screen.
Give it time. Same thing happens to me and then the edge continues with update.
I waited 30 minutes and it didn't work. I turned off the device by holding the button for 10 seconds. The device started up correctly, but the language changed to a different one. After another restart, the update was successful. It works randomly.
I had to force reboot mine to get the update to complete as well.
2 many bugs unfortunately
Had the same issue with the 21.16 update, after forcing reboot, update installed correctly. Thanks for the hint.