We have an install of Mura that is about 3 years old and which as been running in Docker that whole time. It was on Mura 7.3.1 and Lucee 5.3.6. I'd been putting off and putting off doing anything with it because it 'just worked' but it really needed to be running current versions both of Lucee and Mura or Masa.
We rebuilt the docker images with our updated Lucee base images and then by cloning the Masa repo instead of the Mura repo and dropped it in our Docker swarm. It 'just worked' - all sites running, admin logins, everything. Smoothest update we've had for anything in a while!
Thanks guys!