you could try to use the default dex starter and comment the one used:
exec --no-startup-id dex -a -s /etc/xdg/autostart/:~/.config/autostart
#exec --no-startup-id dex --autostart --environment i3
and indeed comment the welcome starter line:
#exec --no-startup-id sh /usr/share/endeavouros/scripts/welcome --startdelay=3