I'm trying to get an idea of how long each step takes while building an image (doesn't necessarily have to be exact, even just me seeing it on the screen is enough), but even with

-ldebug

the output is buffered then dumped immediately, is there a way to do that?

Pants aside, try using BuildKit on a docker CLI run: https://docs.docker.com/build/buildkit/#getting-started that gives timings.

according to this article https://stackoverflow.com/questions/46166293/how-to-measure-docker-build-steps-duration:

--progress=plain

Buildkit worked, thanks