gdm 3.38 with nvidia drivers breaks Wayland support (once nvidia drivers are disabled)

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1899673

I noticed this last week too. But only people switching GPUs like us will hit it, and even then the system is perfectly usable.

This is critical as it corrupts the system configuration data, and more importantly it will stop any Nvidia user to use Wayland whenever it's supported by the closed drivers or switching to free ones.

As per this it needs to be fixed ASAP (when only a limited number of affected versions are around) or it will hit us hard in the future.

This bug was fixed in the package gdm3 - 3.38.1-2ubuntu1

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gdm3 (3.38.1-2ubuntu1) groovy; urgency=medium

  * Merging with debian, containing a new upstream release, remaining changes:
    + readme.debian: update for correct paths in ubuntu
    + control.in:
      - don't recommend desktop-base
      - build depend on libgudev-1.0-dev
      - depend on bash for config_error_dialog.patch
      - update vcs field
      - recomends libpam-fprintd (instead of suggests)
    + rules:
      - don't override default user/group
      - -dgdm-xsession=true to install upstream xsession script
      - override dh_installinit with --no-start to avoid session being killed
    + rules, readme.debian, gdm3.8.pod:
      use upstream custom.conf instead of daemon.conf
    + gdm3.{postinst,postrm}: rename user and group back to gdm
    + gdm3.postinst, gdm3.prerm: don't kill gdm on upgrade
    + gdm3.*.pam: make pam_env read ~/.pam_environment
    + gdm3.install:
      - stop installing default.desktop. it adds unnecessary clutter
        ("system default") to the session chooser.
      - don't install debian/xsession
    + add run_xsession.d.patch
    + add xresources_is_a_dir.patch
      - fix loading from /etc/x11/xresources/*
    + add nvidia_prime.patch:
      - add hook to run prime-offload (as root) and prime-switch if
        nvidia-prime is installed
    + add revert_override_lang_with_accountservices.patch:
      - on ubuntu accountservices only stores the language and not the
        full locale as needed by lang.
    + add dont_set_language_env.patch:
      - don't run the set_up_session_language() function, since it
        overrides variable values set by ~/.pam_environment
    + add config_error_dialog.patch:
      - show warning dialog in case of error in ~/.profile etc. and
        don't let a syntax error make the login fail
    + add debian/patches/revert_nvidia_wayland_blacklist.patch:
      - don't blacklist nvidia for wayland
    + add gdm3.service-wait-for-drm-device-before-trying-to-start-i.patch:
      - wait for the first valid gdm device on pre-start
    + add debian/default.pa
      - disable bluetooth audio devices in pulseaudio from gdm3.
    + debian/gdm3.install
      - added details of the default.pa file
    + debian/gdm3.postinst
      - added installation of default.pa and creation of dir if it doesn't
        exist.
    + debian/greeter.dconf-defaults: don't set debian settings in the
      greeter's dconf db

gdm3 (3.38.1-2) unstable; urgency=medium

  * debian/gdm3.preinst: Add script to replace possibly wrong .conf file.
    In gdm3 versions of the 3.38 series a regression was introduced causing
    the /usr/libexec/gdm-disable-wayland tool to write its supposedly
    temporary gdm file to the persistent location.
    This is particularly harmful for users of the NVIDIA drivers as they
    will get their default config file (/etc/gdm3/daemon.conf in debian and
    /etc/gdm3/custom.conf in Ubuntu) modified for good, making impossible to
    login in a Wayland session (once nvidia driver is disabled).
    As per this, in case of upgrades or install with configuration files
    left, we replace the gdm's daemo...