I have recently encountered an issue using the new modern Advanced Find within our Organization after migrating from an on-premises Dynamics 365 tenant to the Power Platform.
Whenever a system user tries to use an Advanced Lookup field with the modern Advanced Find the Advanced Lookup modal will open behind the Advanced Find out-of-focus and the system user will not be able to select records from the Advanced Lookup. Please see my screenshot below where I use the Website table as an example. This issue seems to affect all tables, regardless if they are managed, unmanaged or custom tables added by us.
Has anyone else encountered this issue?