It was a forced breaking change, in particular, as stated in that linked incident the user search over custom fields was restricted in some tenants in order to ensure that basic user search functionality could be restored. As also mentioned in the incident there was an email address that could be used by impacted tenants in order to inquire about the possibility to have those restrictions lifted if they had created the tenant account before the incident. I see that you or someone associated with your tenant domain has used that communication channel and that the situation is now addressed, however, wanted to give an update here in case someone else faces the same situation which in that case the recommended approach would be to indeed use the communication channel listed in the incident.