Mac Mini (M1) dual display doesn't work.

Another possible problem is the age/quality of your HDMI cable. Although they look the same, some only do 30 Hz, whereas others do 60 Hz. Some are called “active” versus (I suppose) “passive”. It is all gobbledygook to me.

I had the M1 8gb ram I used shorter HDMI cables 1 meter in length they worked dual monitor i have 42inch HD and 32 inch 4K no problems i up graded to 16gb ram as the 8gb kept freezing with the colorful spinning wheel of dead

Buy the Apple HDMI to DVI Adapter, for $29 bucks and see if that works. if it doesn't, you can just return it. I had your setup before: VGA cable to the apple official VGA Multiport adapter. All kinds of problems. My monitor also has an HDMI port, so I bought that adapter and 99% of my problems went away. I still get the occasional snowy image, but a quick monitor refresh rate change will fix that.

Basically: try a different adapter. Also, you can just wait. Sounds like 11.2 is fixing problems for people.

LUCK!

I have a 16 GB M1 Mac Mini running three monitors in a flight simulator. One monitor, which is actually a TV, is connected via HDMI on the Mac to HDMI on the TV. The second monitor is connected via Thunderbolt on the Mac to a Bellini adapter, and then VGA to VGA on the monitor. The third monitor is connected via USB-C on the Mac to Stratech part number USB32HDDVII to VGA on the monitor. The latter requires the DisplayLink driver, which you can download from Startech’s site. The driver must be running.

I am using Samsung Dual screen monitor. One port is HDMI to HDMI (Screen 1) and the 2nd screen is attached to macMini M1 with a USB C to Display Port. I don't get a flickering screen, but I get only the Screen 1 (HDMI to HDMI) that starts up. The screen 2 (USB C to Display Port) does not turn on. After Screen 1 comes on, I need to pull both the cables out i.e. the HDMI and the USB C out of the MAcMini, then wait for 2-4 seconds and put back the USB C to Display Port cable in, then the Screen 2 lights up, after Screen 2 lights up, then input the HDMi cable in to the MacMini - then Screen 1 come on - such a pain. I have to therefore make sure my MacMini in never sleep mode. However, when I switch off the MacMini, I have go thru the same process again. I read a blog somewhere that Apple is aware of the problem, but has not provided a solution.

I have one 20 point touch screen hdmi>hdmi and one Samsung screen usb(display port)>usb c .

I had to stop the Samsung monitor from auto detecting the input by cycling to dedicating the usbc(DisplayPort ) as the manual fixed connection then I shut down the Mac mini and then restarted and kept my finger pressing the power button for 10 seconds and when Mini restarts to a recovery. menu shut it down . Restart it and see if both fire up. If they don’t go into login preferences and gat the Mac to auto login. Shutdown , start the Mac Mini up again and see if both monitors fire up. That worked for me after installing 11.2

I suspect that there are a lot of bad cables out there, as so many people seem to have trouble linking the M1 Mac Mini to two monitors. Mine is successfully driving three monitors in a flight simulator. The details are as follows: X-Plane 11.53r1 on a 16 GB M1 Mac Mini (494 GB storage) connected to (a) Dell model 2007 FPS monitor (1600 x 1200 @ 60 Hz via VGA on monitor to VGA/DVI-I adapter to Startech.com USB 3.0 Dual Head Graphics Adapter to USB-C on Mac Mini), and (b) to a Westinghouse TV model LDD2240 (1920 x 1080 @ 60 Hz via HDMI to HDMI), and (c) to a Flatron W2252TQ (VGA on monitor to Belkin VGA/Thunderbolt adapter to Thunderbolt on Mac Mini).  Startech’s DisplayLink driver was loaded and activated. OS is Big Sur 11.3. Logitech Saitek Yoke, Power Quadrant, Rudder Pedals, and Radio Stack. Flight Velocity elevator trim.

Check cable length and limit it to 1m.

Use short HDMI 1 meter cables 3 feet for USA it worked for me

11.3 is fine, use apple cables not cheaper copies.

Hahaha. Apple advisor had me purchase this adapter from their site and see if it works. I’ll know when it arrives tomorrow.

https://www.apple.com/shop/product/MUF82/usb-c-digital-av-multiport-adapter?fnode=8a0504c8bbb04c4ada6705eb02728099c7dc2b3b4e1e46282ecf7fe92ed2693c845d237f768939b3e6d14e919aa706674c4815681d4557d95e0eccdf6c34690de3f1a23bc3a1d02ab621e1fcaf5e7d7c8fb343b7da93472d478e5061971bfdf9

Same problem! Fresh start up or wake from sleep results in either 1) Artifacts on the HDMI directly connected or 2)VGA (via $69 USB-C dongle) reverts to 1024x768 resolution and refuses to go higher. Unplugging then re-plugging cables completely fixes the problem and everything is perfect... until the system either reboots or goes to sleep. Made a call into apple and we've begun the return process. We'll see how the second unit acts up.

System: Mac mini M1 16GB 512HD, dual dell 1080p monitors.

This has been a pretty frustrating thing for me too. I have an M1 Mini (16GB RAM/2TB SSD) running two BenQ PD2700U monitors. The right monitor is a direct HDMI connection to the Mini. The left monitor is attached via DisplayPort cable to a CalDigit TS3 Plus hub (which is in turn connected to the Mini via Thunderbolt 3). Prior to the 11.1 update, both monitors would flicker, resize, go black, and all sorts of assorted weirdness anytime the machine went to sleep. The only way to correct it involved unplugged the HDMI cable from the Mini and plugging it back in. After the update, the problem seemed to vanish, but has now changed to the monitors both occasionally resizing to a different resolution when I wake them. Turning the right monitor on and off again corrects the problem immediately. It doesn't happen every single time the monitors wake from sleep, but it is'a good percentage of the time. At least I don't have to physically unplug anything now.

Yours is, more or less, what happens to me when using two identical ASUS monitors. But I have now found out something that further confuses me. I have an HP usb-c portable monitor. Just for japes, I plugged it in along side the monitor that is connected directly via HDMI, the same monitor that generally restarts at a 270 degree rotation. What is really weird is that now, both screens behave as you would expect. The HDMI monitor always starts in the proper rotation, even from sleep. So it looks like something about the Thunderbolt port controllers is impacting the HDMI port.

In my case I have an M1 Mini with two identical LG32UL750 displays attached, one using the HDMI port, the other over Thunderbolt. When the machine wakes from sleep, it often forgets about the HDMI display (it's not even listed as a display). It also very occasionally, when both displays are active, blanks the display attached over Thunderbolt for a second or so before recovering.

I don't see any pink spots or anything like that, and it's fine on reboot.

In both cases I'm using the cables that came with the displays themselves, and I'm on the latest version of Big Sur (11.1).

I've taken to turning the displays off completely when I'm away from the machine, as turning them on first and then waking the machine from sleep appears to work. Trouble is, if I forget to do that, I end up with only one display enabled and nothing I do in the Display Settings pane of System Preferences will resolve that.