#define USER_PROMPT "An email with a one-time passcode was sent to your email." \
"\nEnter the code at https://aka.ms/devicelogin, then press enter.\n"
Template should be stored in /etc/aad/template.d/, (See: CyberNinjas/libnss_aad#5); or similar; add this to the config file via template_dir.
Source: https://github.com/CyberNinjas/pam_aad/issues/37