External Display Not Detected after upgrading to 12.3 Monterey

In a situation like this I would typically disconnect the device and verify cable is in good condition not pinched or cracked, verify both connectors are in good clean condition not full of dust as well as the corresponding ports on the device and the MacBook. I will then disconnect power from the external device, in this case the monitor do the same with that cable. Once you verify both cables and connections are clean and in good condition plug the communication cable back in to the Mac and then the monitor, connect power to the wall and the monitor, if power plug sparks, that means the ground in your outlet is not proper and should have that addressed by an electrician.

My post was censored since apparently I was ranting (I wasn't), and it wasn't technical enough (fine). So here you go:

using dual Dell displays using TB to DP connection on a 2018 Mac Mini. Since the 12.3 update, only one monitor works at a time, no matter how many times I power cycle the mac and displays and connect/disconnect them. Other forums seem to corroborate the issue so it appears to be widespread.

I have the same issue with a 2018 Mac Mini. I'm running two LG displays and found out from another post via REDDIT that, under 12.3, if you connect one display using BOTH HDMI and USB-C to DP and the other using USB-C to DP then it works. It's still a bit random in the plus/unplug cycle on each monitor to get them both to fire up but persevere and both do eventually come on. How reliable the restart cycle will be I'm not sure yet - only just got it sorted. Why on earth this works I don't know but it does.

I've always found the 2018 Mini to be a bit flakey with displays; I originally couldn't get the monitors to work via one on HDMI and one USB-C to DP and had to buy another USB-C to DP cable.

My 2018 mac mini was very flakey when it comes to dual displays back when I bought it, but it has been rock solid from around 2020 to... yesterday.

It would appear Apple only tested 12.3 with Apple monitors, and most likely, only one at a time. I have perused other forums, the issue has been there since the 12.3 betas (I can find posts dating back to January), but apparently the issue hasn't percolated to the mothership yet.

Yes, usage of non-Apple displays seems to be broken - again. I have the same issue with my 2018 Mac Mini