Comment 5 for bug 1762391

According to my tests GDM works as expected - checking groups the user belongs to on different terminal emulators (e.g. xterm) proves that the /etc/security/group.conf groups are correctly applied.

The problem in this case affects gnome-terminal alone (and the problem is present also if using e.g. LightDM instead of GDM).

This is related to the way gnome-terminal-server is started via DBus and executed under systemd --user. It is started under the systemd-user PAM service, so pam_group entry should be added to /etc/pam.d/systemd-user. The problem is systemd will never apply pam_group settings because it does not call pam_setcred.

The issue is reported to systemd along with a PR fixing it:
https://github.com/systemd/systemd/issues/11198