'apt remove yaru-theme-gnome-shell' removed 'ubuntu-session' and broke 'gdm.service'

[climagabriel]

# uname -a
Linux pqr 6.17.0-6-generic #6-Ubuntu SMP PREEMPT_DYNAMIC Tue Oct  7 13:34:17 UTC 2025 x86_64 GNU/Linux

# cat /etc/*release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=25.10
DISTRIB_CODENAME=questing
DISTRIB_DESCRIPTION="Ubuntu 25.10"
PRETTY_NAME="Ubuntu 25.10"
NAME="Ubuntu"
VERSION_ID="25.10"
VERSION="25.10 (Questing Quokka)"
VERSION_CODENAME=questing
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=questing
LOGO=ubuntu-logo

apt remove yaru-theme-gnome-shell
The following packages were automatically installed and are no longer required:
  gir1.2-gnomeautoar-0.1  gir1.2-gnomedesktop-3.0  xwayland
Use 'sudo apt autoremove' to remove them.
REMOVING:
  ubuntu-session  yaru-theme-gnome-shell

Resulting in this on reboot:

Nov 20 12:48:33 pqr systemd[1]: Starting gdm.service - GNOME Display Manager...
Nov 20 12:48:33 pqr systemd[1]: Started gdm.service - GNOME Display Manager.
Nov 20 12:48:33 pqr gdm3[3133]: Gdm: GdmSession: no session desktop files installed, aborting...
Nov 20 12:48:33 pqr systemd[1]: gdm.service: Main process exited, code=killed, status=5/TRAP
Nov 20 12:48:33 pqr systemd[1]: gdm.service: Killing process 3157 (gdm-session-wor) with signal SIGKILL.
Nov 20 12:48:33 pqr systemd[1]: gdm.service: Killing process 3163 (gdbus) with signal SIGKILL.
Nov 20 12:48:33 pqr systemd[1]: gdm.service: Failed with result 'signal'.
Nov 20 12:48:33 pqr systemd[1]: gdm.service: Triggering OnFailure= dependencies.
Nov 20 12:48:34 pqr systemd[1]: gdm.service: Scheduled restart job, restart counter is at 1.

apt install gnome-session fixed it on reboot