This appears to be the key. I did go though and remove as many docker-xxx packages as I could think of earlier, and it made no difference.
This time, docker installed and started after I ran the find lines.
Discourse is updating it’s base now… We’ll she
I was (still am) pondering moving to ubuntu purely because my exisitng setup on centos seems to be very fragile. Anytime I try to update discourse, I end up with a broken container, or a docker that won’t start.