Thank you for both your responsese, greatly appreciated. @DTS Engineer, the app we're developing is for the iPadOS, running on iPad Pros.

@DTS Engineer, Thank you for the confirmation and link, does this mean that both us and our client would need to be members of the Apple Business Manager?

@DTS Engineer One other question, we are assuming that if we went through the app store process, even though it's not a public facing app, we would still need to go through the app store verification stage?