Is the package manager a significant amount of time compared to setting up containers, running tests etc? (Genuine question, I’m on holiday and can’t look up real stats for myself right now)
Anecdotally unless I'm doing something really dumb in my Dockerfile (recently I found a recursive `chown` that was taking 20m+ to finish, grr) installing dependencies is longest step of the build. It's also the most failure prone (due to transient network issues).