Problem assigning 'privileged administrator roles' to Service Principals using the portal

Question

hello,
I noticed today that I am not able anymore to assign 'job function roles' or 'privileged administrator roles' to service-principals using the Azure Portal.

To do that, first I select the object I want to adjust the RBAC config for (in my case I want to assign the role 'Contributor' at the subscription level, then:

• I select 'Access Control (IAM)
• then, "+Add" > "Add role assignment"
• then, from the page "Privileged administrator roles" I choose "Contributor"
• then I click Next" to move to the selection of the subject I want to assign the role to
• then I make sure that the radio "User, group, or service principal" is the one selected
• then I click on "+Select members" which opens a panel to choose the subject(s)
• And finally, I notice that in the list of available members the service-principals I have created do not show up.

Note that when I use the "az" CLI commands I can successfully assign this role to the Service Principal.
Note also that I did this very same operation using the Portal just a few days ago and this worked just fine.

Is there anything I do wrong? Or is there a recent update applied which could explain this new (buggy) behavior?