OT: Dell displays

Not that model, but from a quick shufti of the manual, I'd expect the 4x USB2 ports to work, once you have a USB connection to the PC, you are using a USBC->USBC cable?

Are you sure you're using a USB-C cable that supports super speed? Some of the cheap ones are only USB2 for example. If the cable supports 5/10/20 Gbps then that should do it.

If you're getting video it suggests the cable is good for super speed, which makes it puzzling why USB 2 isn't working.

You could probably also try an HDMI/DP cable and then you just need a USB-C cable with USB2 support for the USB ports.

Theo

Yep, that's what the doc says to do, so that's what I does. It's a new M1 Mini I'm connecting to.

"Cough" (4,3)

The USB-C cable I was trying with is the one that came with the display. I did try both cables at once but Big Sur didn't like that at all.

I have a Dell P2314T, USB cable to PC with display and audio via HDMI. The 2 USB sockets works fine, Audio to display via HDMI and then out through the displays phonos works but was a bit of a pain to setup.

Can the M1 Mini support both the display and downstream USB ports from its USBC port?

This is prolly the crux of the matter. Perhaps I need both cables (USB-C and HDMI) but then tell the display to choose HDMI first.

The display does not have a socket for one of the old square USB-B type plugs.

By contrast my Dell U2518D does have a USB-B socket and its 4 USB ports work fine. That display connects to my intel Mini with USBC at the Mini end, HDMI at the display.

If what you have used is a Thunderbolt cable you could try a vanilla USB-C 3.1 if you have or can borrow one.

I tried that with my iIyama monitor connected to my HD FOX T2 stb connected via hdmi but the audio out of the back of the monitor was awful, so I connect the stb to a Class D Amptastic mini amp via phono's and use a pair of old Phillips computer speakers.