Comment # 15 on bug 1188954 from Felix Miata

Using systemd-networkd instead of wicked or networkmanager makes the (~6s)
difference between KMS module finishing loading soon enough or not.

This is from an xdm startup failing using systemd-networkd:
# journalctl -b -o short-monotonic -u display-manager.service -u
systemd-modules-load.service -g St
-- Journal begins at Sat 2021-01-16 18:26:29 EST, ends at Sat 2021-08-14
16:50:47 EDT. --
[    3.849113] asa88 systemd[1]: Stopped Load Kernel Modules.
[    6.231843] asa88 systemd[1]: Starting X Display Manager...
[    7.383982] asa88 display-manager[651]: Starting service tdm
[    7.384359] asa88 systemd[1]: Started X Display Manager.

This is from an xdm startup succeeding using wicked:
# journalctl -b -o short-monotonic -u display-manager.service -u
systemd-modules-load.service -g St
-- Journal begins at Fri 2021-08-13 23:33:06 EDT, ends at Sat 2021-08-14
17:38:24 EDT. --
[    3.731005] localhost systemd[1]: Stopped Load Kernel Modules.
[   13.312481] asa88 systemd[1]: Starting X Display Manager...
[   13.411758] asa88 display-manager[1013]: Starting service xdm
[   13.412175] asa88 systemd[1]: Started X Display Manager.

All my systems are configured with static IP, without IPV6 enabled, and without
resolvconf of any kind enabled.

It looks like the summary should be:

        display-manager.service starts too soon when using systemd-networkd
or
        using systemd-networkd instead of wicked or networkmanager results in
        systemd-modules-load.service functionally finishing after
display-manager.service starts