Staze, you are exactly right. Profile based device enrollment is still supported. For user enrollment, Account Driven User Enrollment (with Managed Apple Account) must be used.

I suggest filing Feedback on this here: https://feedbackassistant.apple.com -- file to (Enterprise and Education --> Mobile Device Management) and make sure to include iPadOS versions where this occurs and any information about your network (i.e. Global Proxy in place?)

Do you have a an app allow list on the Macs in question?