Hello,
I installed libnss-extrausers today, because I want to sync additional {passwd,group,shadow} with a nfs or rsync server.
I want the extrausers to change their passwords with the default tools. Ubuntu has a module pam_extrausers, which is basicly a copy of pam_unix but it looks at /var/lib/extrausers/{passwd,shadow,group}.

My wish: please add this module to debian

for now it works for me with the pam_extrausers.so from ubuntu..

ubuntu manpage:https://manpages.ubuntu.com/manpages/noble/man8/pam_extrausers.8.html
ubuntu patch:https://git.launchpad.net/ubuntu/+source/pam/tree/debian/patches/extrausers.patch?h=ubuntu/noble