Same experience here. Mac Mini 2018, MacOS 12.3 public release. Monitor connected via USB-C. When powering on with the external drives attached (one TB3 other USB) after the apple logo is shown and boot progresses it ends up with a black screen. After the 12.3 update finished, I was surprised by it. Fortunately I have an external graphics, after I connected it I got the picture out of it - but no chance with the Mac Mini USB-C ports. The external graphics is working OK even after reboot or powerup with everything attached, so I am kinda lucky. I confirm that (when having the picture using the external graphics) by unmouting the USB and TB3 external drives and then connecting the monitor via USB-C I am able to get the picture from it, then I do safe disconnect of the external graphics and connect the other peripherals the picture continues to be delivered over the USB-C connection. Also I saw some suggestions to switch the monitor into DP 1.2 mode - on my I have no such option.