I asked Claude for debugging help. It said - What's actually happening:
You selected "Default Xsession" on the GDM gear icon. GDM resolved that to lightdm-xsession (see line 4789: DESKTOP_SESSION=lightdm-xsession). lightdm-xsession is a generic X11 session wrapper. On your system, it tries to start [email protected] — i.e. a GNOME X11 session, not XFCE. GNOME 49 on Ubuntu 25.10 does not ship a GNOME X11 session anymore — it's Wayland-only now. So that systemd unit doesn't exist. gnome-session then crashes (trap int3 in glibc — an abort), the session dies before it can register, and GDM shows the auth error and drops you back to the login screen. Crucially: this confirms exactly what Daniel was pointing out in the earlier round. "Default Xsession" / "lightdm-xsession" is not your old session — it's a leftover wrapper that's trying to launch GNOME on X11, which Ubuntu 25.10 removed. What your "old session" actually was: Before the breakage, you were most likely logging into either: GNOME on Xorg (which no longer exists in 25.10), or Ubuntu on Wayland / GNOME on Wayland (now the only GNOME option) The "Default Xsession" / "lightdm-xsession" entry you're clicking is a red herring — it was never meant to be a working session on a GNOME-49 system. It only works for you under LightDM because LightDM happens to route it to XFCE via a different mechanism. -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-session in Ubuntu. https://bugs.launchpad.net/bugs/2148808 Title: gnome-session-init-worker crashes with SIGTRAP: Unit gnome- [email protected] not found To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/2148808/+subscriptions -- desktop-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
