bug#73869: Cannot start EXWM without a display manager

[Oleander]

Hello, 
do we have a way to start an X window manager (EXWM in my case) without installing
a display manager? The manual does not cover this subject and so far all
my attempts with the suggestions I collected from the mailing list [1]
[2] have failed. I tried xinit, startx or sx but nothing starts exwm
properly without GDM. I was only able to start exwm with xinit but it
takes longer compared to GDM and when the WM is initialized, it does not
receive any input, it is impossible to move the mouse pointer or type
anything.

[1] https://lists.gnu.org/archive/html/help-guix/2018-07/msg00080.html

[2] https://lists.gnu.org/archive/html/help-guix/2024-09/msg00094.html

My .xinitrc contains:

```
xrdb -merge ~/.Xresources
xsetroot -cursor_name left_ptr
xhost +SI:localuser:$USER
udiskie --tray &
exec dbus-launch --exit-with-session emacs
```

Thanks in advance!