A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.
Do you mean you want to enable Skype for Business for this user in hybrid mode?
Based on my research, you could move a user who was previously migrated from on-premises to Teams back to on-premises. To move users from TeamsOnly mode back to an on-premises deployment of Skype for Business Server, use either the Move-CsUser cmdlet or the Skype for Business Server Control Panel. For more details, you could refer to: