So, there might be a misconfiguration in my docker instance as I tried four of those cups dockers available on docker hub and they all produced the same error
That would suggest there is something residual from each install, if I do docker diff cupsd on that olbat/cups I get this;
so I then do ls -l on /etc
based on the above output C at the beginning of /etc/cups must refernce container, so it's not written to the system.
If you had access to a config file in /etc/cups then that must have been residual.
I'm an IT professional (cyber security currently with 10 years of sys admin) so you can trust that I have a rough idea what I'm doing
TBH more tech nerds on here the better, me I try and work on a process of elimination to try and help, I also have VM with omv5 to try out on which is where I have this docker deployed