Software throughput may not be quite so standardized, and that might prevent you from applying every single nitty gritty specific improvement that someone found

Software throughput may not be quite so standardized, and that might prevent you from applying every single nitty gritty specific improvement that someone found in a maufacturing-oriented LSS implementation. But there are still things you can meaningfully quantify. The thing that Kanban software development chooses to focus on, lead time, would be my top candidate. That seems universal. I'm guessing most others would be team-specific things that come out of a DMAIC analysis. If you've got a problem with too much rework due to team miscommunication, the specifics of how you measure that are going to depend a lot on how your team defines rework in the first place.