For a couple of months, both Twitter and GitHub logins to the forum have been broken.
Twitter logins are fixed now and should work as before.
GitHub logins are also fixed, but previously created logins will no longer work. If you are affected, you can contact me at email@example.com, and I’ll try to see if we can recover it. Alternatively, feel free just to create a new account
I understand the cause of both breakages and I don’t expect them to happen again now.