Frozen mouse after software update/reboot. Cannot login

After running a software update and reboot, I cannot login anymore:
I see the MATE-logo in the center of the screen and the mouse pointer in the middle. But I cannot move the mouse-pointer to the login-window.

The os is 18.04.6 LTS . File in /boot with date of today are initrd.img-5.3.0-1042-raspi2 and initrd.img-5.3.0-1041-raspi2.

Remote login from another host works.

How can I fix this problem?