After executing the ubuntu updates as already performed many times the X graphical environment does not boot anymore.
The latest update installed kernel 126.96.36.199 in grub.
When selecting an older kernel in grub 188.8.131.52 the machine boots correctly in X.
I am using nvidia legacy drivers:nvidia-utils-390 390.116-0ubuntu0.18.04.1
Which should be the latest. How can this be resolved?