Here is a collection of resources I found useful when learning about setting up, and troubleshooting, Windows Autopilot Hybrid Join.
First, why you may want not to 🙂
Deliver us from Hybrid
https://call4cloud.nl/2021/03/deliver-us-from-hybrid
Second, resources for setup and troubleshooting
Configure Autopilot Hybrid Azure-AD and ADDS Domain Join
https://www.thelazyadministrator.com/2020/01/16/configure-autopilot-hybrid-azure-ad-and-adds-domain-join/
Trying out Windows Autopilot User-Driven Hybrid Azure AD Join – By Michael Niehaus
https://docs.microsoft.com/en-us/archive/blogs/mniehaus/trying-out-windows-autopilot-user-driven-hybrid-azure-ad-join
Autopilot Intune Connector for Active Directory – By Peter Egerton
https://morethanpatches.com/2020/06/24/autopilot-intune-connector-for-active-directory/
Admins Experience: Deploy Hybrid Azure AD-joined devices by using Intune and Windows Autopilot – By Mingzhe Li
Admins Experience: Deploy Hybrid Azure AD-joined devices by using Intune and Windows Autopilot – Microsoft Tech Community
Autopilot hybrid domain join failure (80070002) – By Steve
https://www.risual.com/2021/04/autopilot-hybrid-domain-join-failure-80070002/
Troubleshooting Windows Autopilot Hybrid Azure AD Join – By Michael Niehaus
https://oofhours.com/2020/07/19/troubleshooting-windows-autopilot-hybrid-azure-ad-join/