After further investigation, the right /etc/gdm/custom.conf is present in the squashfs.
Unfortunately, /usr/share/initramfs-tools/scripts/casper-bottom/15autologin is erasing /etc/gdm/custom.conf with autologin values and so, default session setting is gone away.
I'm trying to handle this more gracefully in /usr/share/initramfs-tools/scripts/casper-bottom/15autologin.
After further investigation, the right /etc/gdm/ custom. conf is present in the squashfs.
Unfortunately, /usr/share/ initramfs- tools/scripts/ casper- bottom/ 15autologin is erasing /etc/gdm/ custom. conf with autologin values and so, default session setting is gone away. initramfs- tools/scripts/ casper- bottom/ 15autologin.
I'm trying to handle this more gracefully in /usr/share/