I’ve successfully installed and configured unix duo, but the prompt on the GDM login screen seems to overlap and doesn’t look very good. It appears to work correctly on other display managers like LightDM, but is there any way to make this look better for GDM?
I’d like to add to this. The issue seems to be related to GDM 3.36 changing how it displays PAM_PROMPT_ECHO_ON messages. The Gnome developers seem to think multiline messages should use PAM_TEXT_INFO. There is a issue in the Gnome Shell repository from a year ago here GNOME Shell 3.36 broke compatibility with PAM modules, can not show multiline messages. (#3627) · Issues · GNOME / gnome-shell · GitLab