Looks like the BIOS update fixes it.  I found an older StarTech DP to HDMI adapter that worked, which let me init the system and update the BIOS.  I imagine a straight DP monitor would've worked, too.  After the BIOS update to 2.7, the Moread DP to VGA adapters worked.
I have new optiplex 3090 with two DP ports...When i try to connect to older monitor with vga / hdmi connector, using DP-VGA  or DP-HDMI adapter i get no picture on monitor. FInally after trying different cables/monitors/adapters i tracked problem to BIOS 2.5.1 (from june 2022)...After i made downgrade of bios to 2.4.0  now it works fine..  Does anyone have the same problem?
Optiplex 3090 no video signal