My boss have several domains at GoDaddy. For example, two of them are domain1.com and domain2.com. He wants to transfer the email for domain2.com to a different M365 and get rid of domain1.com altogether.
He wants to know what to do to make that possible. The email for both domains is managed by the domain1.com account so he cannot do anything with it at GoDaddy. But if he can transfer the email for the domain2.com domain to a client tenant, he can have full control over it, which is what he needs.
So in the end, GoDaddy would keep the domain and he would control the M365 tenant for domain2.com.