I have got the same issue, Domain joined devices to my AADDS domain, AVD and both on premise devices but I cannot Hybrid AD join so we can get the automatically enrolled to Intune.
For the few physical machines joined to the domain I wanted to use Autopilot with Hybrid AD join to build and manage the devices but without the hybrid AD join capability I'm up the creek without a paddle. having to Autopilot with AAD join, remove from AAD then domain join. this is required as the on premise app relies on domain services to function.
Microsoft, Please give us the hybrid AD join and Auto MDM capability in AADDS.