Mac OS 12.3 Beta and Monitor Problems

I have had ongoing issues with this since I bought my 2018 Mac Mini (Intel) and with every OS since then. There was a set of firmware updates in early 2019, and also in the Big Sur releases that helped, but the issue appears to be back for me (12.1.* and 12.2 public releases).

I have 2 X 4K Samsung screens, one directly connected by HDMI and the second connected through an OWC Thunderbolt 3 Dock using USB-C(TB DisplayPort)-to-HDMI.

The only thing that seems to work reliably for me is to disconnect the dock monitor, then power on the computer, then reconnect the dock monitor after a successful boot.

If I have both connected when the machine is powered on, the internal HDMI fails to work - Every time. I have a Feedback report FB9845580 showing the Console Log errors when I try to connect the internal HDMI.

Once this happens, I have to shut down the computer, disconnect the external dock monitor, and even then the internal HDMI port doesn't reliably come up. When that happens, I must do a PRAM reset to restore the internal HDMI.

So my suggestion: 1: Disconnect any external dock you have after you power off. Then connect the HDMI and power on. 2: Disconnect external dock/ monitors. Connect the HDMI to internal monitor. Then reset PRAM. Hold CMD-OPT-P-R (all 4 keys) when machine is off. Power on machine. Continue holding all 4 keys until machine auto-reboots. Then release the keys. I found this was required in some of the earlier betas to restore the HDMI. Once it finishes booting, you can reconnect any other external monitors.

Also, please put in a Feedback Report so Apple Support gets the detailed log messages. Maybe that can help with finally resolving the issue for us Mini 2018 owners!

You should see Kernel messages related to IGFB in the Console log when the issue occurs. Hope this helps.

I have this exact problem with my 2018 Mac Mini. It seems to happen with this particular model. Booting with nothing attached (and indeed resetting PRAM) seems to work, but it is a chore… Still not fixed in beta 4 :-/

Another one here ... also Mac Mini 2010 (bought 2020) with the exact same behavior as described above ... this started after i updated to 12.3 yesterday.

LG 32" 16:9 Monitor connected via HDMI Philips 49" 32:9 ultrawide Monitor connected via USB3/DP Adapter

Native Screen Resolution on 49" was recognized anymore and after some reboots now it seems as if the mac does not even see the connected Philips monitor anymore. Only the HDMI Output works.

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.

I'm having ongoing similar problems with the Mac mini 2018 I got two years ago (in 2020). For these two years hdmi and thunderbolt cablr both leave the screen unable to turn on after startups from turned off state, or starts from sleep state. The latest release of macOS 12.3.1 seems to actually have fixed the thunderbolt connection part such that the screen turns on properly (tested a few days for now, it seems stable so far). However with 12.3.1 the hdmi connectivity is not fixed and the problem is still there; I assume hdmi connectivity is not addressed (usb-c/thunderbolt is). But the bigger problem with 12.3.1 now is the computer is "half bricked". Many of the times the computer freezes halfway or a few minutes after boot. And when it freezes it reboots after awhile and then after finally being able to log in it complains about some system extension being unloaded, and that it saw panic mode. Mind that I had the OS completely replaced with a fresh macOS install just a few days ago when this same computer came back from Apple support. I'm so tired of this Mac Mini 2018 joke that has been haunting me for two years.