Coin, Thanks for the pointers to the topics!
I get the Docker version as 19.03.13. I then go to update the opertaing system with
sudo apt update && sudo apt upgrade -y 3
and the update gets stuck at…
Waiting for cache lock: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 10528 (apt-get)… 454s
with the number of seconds increasing.