My job title is ML Engineer, but my day to day job is almost pure software engineering.

I build the systems to support ML systems in production. As others have mentioned, this includes mostly data transformation, model training, and model serving.

Our job is also to support scientists to do their job, either by building tools or modifying existing systems.

However, looking outside, I think my company is an outlier. It seems in the industry the expectations for a ML Engineer are more aligned to what a data/applied scientist does (e.g. building and testing models). That introduces a lot of ambiguity into the expectations for each role in each company.