KDE now uses OAuth2 Authentication via its own Phabricator Instance on http://phabricator.kde.org, and moves as such away from the former Openid/Identity/plain MediaWiki login. The accounts are synced from identity, even though they need to be activated on Phabricator.
Due to its former mixed nature the wiki accounts are probably not correctly linkable to the new login system. Here are some hints on how to fix the problem.
Accounts that already worked from identity should now seamlessly work as well. Unless you have changed your username on Phabricator and/or your primary mail address.
In that case someone with admin access needs to go to the DB, search the Phabricator username in the phab_user table and replace the mail address in the eu_email column with the current primary mail address on Phabricator.
The same table needs to be changed in case of a new username.
Those accounts are taken down. Not really deleted, but it is not possible anymore to log in with OpenID, neither does the system anymore know which OpenID belongs to which MediaWiki User.
In that case, open a new Account and request a User Merge with your new Account name, the old Account name and mail address.
It is not possible anymore to use the simple MediaWiki login. BUT you can login with your Phabricator account and when you do that, you get asked if you want to create a new account or link to an existing account. Simply enter your former username and password and from now on you can login with your Phabricator account to your old MediaWiki account.
Due to an unknown problem part of the ported identity accounts had no full mail address, but the first letter from it. This leads to some problem when trying to login, because one of the sources of identifying your account is your primary email address you have set in Phabricator.
What should i do?
In case you are sure you already had an identity account on the wikis which worked, but you are presented with a window where you are supposed to select either a new account or an existing one, please contact the sysadmins. Then the database needs to be filled with your primary mail address before you can login.