Hi,
I've tested the login with my own Gotosocial instance (
zlatko(a)social.zlatko.dev) as well as with my pixelfed.social account
(zlatko@), I never got any DM with the Auth code.
Happy to help troubleshoot if I can (ee.g. I can look into the logs on the
GTS instance).
Also it's not a big deal, if you're busy or don't want to deal with this
now.
Zlatko