Breaking: #68081 - Ext:openid moved to TER¶
See Issue #68081
The former core extension
openid has been removed from core code
and is now available as optional extension from the TER.
Login to TYPO3 backend via openid fails until the extension is installed from TER.
Instances using backend login via openid.
An upgrade wizard in the install tool can be use to download and install the extension.