In my work (academia, libraries), I think most folks most often use “stakeholder” as a general term in collaborations and partnerships, following the definition for “one who is involved in or affected by a course of action” (Merriam‐Webster). In our academic library community, some folks use “customer” to describe our internal interactions, which is a problem because that implies only a transactional, financial exchange: “one that purchases a commodity or service” (Merriam‐Webster). Folks need to be engaged in meaningful work in meaningful ways, and that includes through relationships with colleagues, partners, collaborators, stakeholders, and other related community members, which includes various publics. We need our language to best represents our work, including the complexity of our relationships and impacts.
For the generic, the term and concept of stakeholder is useful for less/non-defined partnerships and collaborations, where the role/nature of the interaction is not necessarily one of true collaboration or partnering, but where folks are involved/affected by the course of action. I have also heard pushback on stakeholder, because it is a term that comes from business. I hear those concerns. I still find the term useful as a generic, in part because stakeholder comes from business ethics and has a socio-political approach (see Wikipedia on “Stakeholder theory“). Stakeholder allows me to quickly frame concerns in terms of supporting each according to their impacts and needs.