https://docs.microsoft.com/en-us/azure/lighthouse/how-to/onboard-customer#deploy-the-azure-resource-manager-templates

So far when testing this out, we've been using AOBO from our CSP Partner tenant to a customer tenant, and it seems to work.
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@o-l-a-v, thank you for reaching out. We are looking into this and would get back to you soon on this thread.
@o-l-a-v As per document, user of the customer tenant can deploy ARM template. As per my understanding user can be AOBO or any user who has Owner role.

@JnHs Can you please provide your insights on the same?
Hi @o-l-a-v - sorry for the delayed response. Yes, any user with AOBO access can onboard a subscription. This is mentioned on our CSP topic https://docs.microsoft.com/en-us/azure/lighthouse/concepts/cloud-solution-provider#azure-delegated-resource-management but I'll clarify this in the onboarding topic as well.
I've added this info to the topic, will close this now - please let us know if you have further questions! #please-close