Some time ago, the permissions scheme in Azure Purview changed and the collection level was introduced as a level of permission. (documentation – Access control in Azure Purview)
With that, the root collection and its assigned administrators get more and more important. The permissions in Azure Purview are configured in Purview Studio (Collections -> select a collection -> Role assignments).
What I found out today, is that you can add a Purview Root Collection Admin directly in the Azure Portal. Open you Purview account, and select the Root collection permission menu entry.
Select one member account and add it to the list of collection administrator.
Happy permission management,