Hi,

I just got hit by a similar problem.  I've got .xinitrc in my home directory
and no .xsession file.  The former just invokes startfluxbox.

Now after guix system reconfigure, gdm got selected as login manager.
After I log in at the gdm prompt,  it enters an endless loop, switching
terminals with almost no delay--which makes further debugging difficult.

I *think* I saw an authentication failure after I typed in my user name,
but I can't be sure.  It doesn't ever ask for my password.

I'm writing this from a recovery shell which I entered like the following:

* Reboot
* Let gdm start
* Do NOT log in (if I did, it would endless-loop the machine)
* Press Ctrl-Alt-F2
* on the text console, invoke "ps -ef |grep xorg" and type the command line
so shown again, but insert ":1" as the first argument.
* Press Ctrl-Alt-F3
* Invoke:
  DISPLAY=:1 startfluxbox
* Press Alt-F8

I have the following suggestions for improvements:

(1) Please back off after trying to login so one can actually debug things.
If the login doesn't work on the first try it won't work on the next 245 tries
in the next second either.
(2) Please have a failure fallback that at least returns you to gdm instead of
looping forever.
(3) If there is an error message plase show it in a dialog box--
there's xdialog and zenity that allows you to show a dialog box easily.
(4) Please honor .xsession and .xinitrc if it's there
(5) Please make gdm state the key to use in order to select a session type.
I've still got no idea how to select a different session type in gdm.