Mac mini (M1, 2020), and two screens

https://www.apple.com/mac-mini/specs/

"One display with up to 6K resolution at 60Hz connected via Thunderbolt and one display with up to 4K resolution at 60Hz connected via HDMI 2.0"

The Mac mini supports only one display via USB-C even though there are two USB-C ports, so it is unlikely to support daisy-chaining two displays from one port. You can use the Mac mini's HDMI port for the second display.

If the display has controls to select inputs you may be able to connect the second display to the Mac mini's HDMI port and simultaneously have a daisy chain connection to the first display. Then to switch between the Mac mini and the laptop you would have to move just the first display's cable cable and change the input selection on the second display

The display does have input selection, and you may be able to use one of its auto-select modes.

https://downloads.dell.com/Manuals/all-products/esuprt_electronics_accessories/esuprt_electronics_accessories_monitors/dell-u2421e-monitor_User%27s-Guide_en-us.pdf

I think there is a setup that will work automatically as long as the Mac mini is off whenever the laptop is connected.

Set both displays to auto-select the USB-C input.

Connect the Mac mini to the USB-C input of the first display and the HDMI input of the second.

Connect the laptop to the USB-C input of the second display and a DisplayPort cable from the DisplayPort Out of the second display to the DisplayPort In of the first.

With the Mac mini on, and the laptop disconnected, the first display should auto -select the Mac mini on its USB-C port, and the second display, seeing no USB-C signal (because the laptop is not on or connected) will use its HDMI port (from the Mac mini).

With the Mac mini off, and the laptop connected, the second display should auto-select its USB-C input (the laptop), and the first display, seeing no USB-C signal (the Mac mini being off) should use its DisplayPort input, thus daisy chaining from the laptop via the second display.

The USB out ports of the first display can be used for peripherals for the Mac Mini, those on the second display for peripherals for the laptop.

Hi there,

I've recently purchased an M1 Mac mini and have two A1407 27" Thunderbolt screens. One is connected via thunderbolt 2 to the back of the Mac mini's Thunderbolt 3 port using a dongle from Apple.

I want to connect the second A1407 Thunderbolt Display via HDMI from the Thunderbolt 2 display port to the Mac mini's HDMI port. Can anyone help with what cable or dongle I would require with a link?

After hours upon hours of research, and being sure I had the right adapters from users who were able to get the Cinema display to work via HDMI port on the mac mini, I'm inclined to give a plus 1 to Malcolm's claim. I only wish I had seen his post before wasting so much time. If anyone else was able to find some magic, I'd love to hear how. I now have a very expensive boat anchor to get rid of. (At least the first one words via USB-C.).

Doesn’t look like a dealbreaker. Find out and let us know?

It should daisy-chain wth either a DisplayPort cable or USB-C cable, but auto-input may behave differently between the two types of cable. You'll just have to try it.

If both the Mac mini and the laptop are connected and turned on, the first display should connect to the Mac mini and the second to the laptop.

There is no way to make a Thunderbolt display work from a HDMI port.