X11 on Pi 4

I'm trying to get X11 runing on the Pi4.
So far I don't get a signal on the screen.
I'd tried both HDMI ports.
FreeBSD mentions:
VT(efifb): resolution 592x448
...
fb0: <BCM2835 VT framebuffer driver> on simplebus0
fb0: keeping existing fb bpp of 32
fbd0 on fb0
WARNING: Device "fb" is Giant locked and may be deleted before FreeBSD 14.0.
VT: Replacing driver "efifb" with new "fb".
fb0: 592x448(592x448@0,0) 32bpp
fb0: fbswap: 1, pitch 2368, base 0x3eaf5000, screen_size 1060864


On a Pi3B with the same screen:
VT(efifb): resolution 1280x800
...
fb0: <BCM2835 VT framebuffer driver> on simplebus0
fbd0 on fb0
VT: Replacing driver "efifb" with new "fb".
fb0: 1280x800(1280x800@0,0) 24bpp
fb0: fbswap: 1, pitch 3840, base 0x3e90c000, screen_size 3072000

Is there some kind of initialisation missing from u-boot?
I noticed that raspbian on the Pi4 also leave the screen disabled
until X starts.
Unfortunately starting X on FreeBSD doesn't change anything.

-- 
B.Walter <bernd@bwct.de> https://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.