I have enabled login again and added the following login hint:
"Login via your Roundup account on bugs.gnupg.org has been disabled due to the migration to Phabricator. We apologise for any inconvenience caused. If you have previously used your Roundup account in this wiki, you can request a new password using the link above."
I had to enable the previously used textcha (text captcha) again. If you don't want to enter the answer every time you do an edit, someone already in the https://wiki.gnupg.org/TrustedEditorGroup can add your login name to the list to disable the textcha for you.