As you may already know, it has been announced that Skype for Business Online will be retired from Office 365 on July 31, 2021.
With this move, some administration capabilities are already being retired.
The ‘External Access’ setting for Skype for Business in the Office 365 Administration portal, available in the ‘Settings\Services & add-ins\Skype for Business’ blade, will be retired
Instead start using the Teams administration portal (https://admin.teams.microsoft.com) to manage federation using the ‘Org-wide\External Access’ blade
