What are significant UX KPIs for an enterprise product?

Most KPI lists I have found (like Google's HEART/GSM model) assume a free user - one that can show up to use your product, and then choose to stay or go based on how pleasant the experience is, and how useful the tool is.

Obviously, enterprise UX is not like that. There's no bounce rate, or retention issues, if the employee is required to use the tool. And key tasks tend to be performed very quickly by users who have been trained thoroughly.

So what empiric indicators can I collect for an enterprise product, and improve upon with better UX?