GPi Case 2 - Screen stays black on V > 8.0

[scesoft]

Hi all,
I exchanged my CM4 Module with EMMC to a CM4 Lite.
Wanted to use the SD Card slot and now finally after 1 1/2 years i got a CM4 lite.

1. attempt:
   I flashed Recalbox 8.0 to SD Card and installed the Display patch.
   Hurray -> Recalbox booted and i could configure it on the GPi 2 screen.

2. attempt (now it gets ugly):
   I flashed Recalbox 9.1 to SD Card and DID NOT INSTALL the Display patch (regarding documentation not needed).
   Inserted SD to GPi 2 -> Nothing -> stays black

3. attempt:
   I flashed Recalboc 8.0 again and configured it.
   Then it updated to Recalbox 8.1.1
   Reboot
   Screen stays black

I have no clue what to do now
Wanted to change to recalbox, but can't get it working.
Retropie works.
Recalbox Version < 8.1 works.

CM4 Module is placed OK (Retropie and older Recalbox works)

Ahhh - I have no Dock so i can't test anything via HDMI

Recalbox is definitely booting, because a hardware.log is created on th SD card, but screen stays black/empty

Does anbody have a tipp what i'm doing wrong?

kind regards,
Peter