2. Do this things on your BusyBox Shell, kill the process id, change 21123 with displayed process id after you do ps
# ps | grep dmsetup | grep -v grep
21123 root 29466 S dmsetup create -r osprober-linux-sdc9
# kill 211233. Back to installation windows by pressing ctrl-alt-F1
Wait a moment, your installation will continue
You can read the full explanation as I found it at https://jrs-s.net/2019/05/31/ubuntu-18-04-hung-at-update-grub-66/
