U2715H, daisy chain setup

Although there may be non-validated "workarounds", Dell will not support a DP 1.2/MST daisy chain if the PC out port is HDMI/DVI/VGA.

We can see from the online U2715H User's Guide pages 25/26 that the suggested DP 1.2/MST daisy chain is using a PC DP out port. But, a PC USB Type-C out port should also work.

PC TB3/USB-C out port --> TB3/USB-C to DP cable --> #1 U2715H DP in port (left) (Menu- Display- DP 1.2 Enable)

#1 U2715H DP out port (right) --> U2715H DP to mDP cable --> #2 U2715H mDP in port (center) (Menu- Display- DP 1.2 Disable)
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#1 U2715H DP out port (right) --> DP to DP cable --> #2 U2715H DP in port (left) (Menu- Display- DP 1.2 Disable)

@nomoreusernames  Daisy chaining requires that you be using a native DisplayPort signal, so if you're using HDMI to connect to the first display, that's the issue.  However, if your USB-C port supports video output, which not all USB-C ports do, then you can use a USB-C to DP cable to connect to the first display in the chain, and then you'll be fine.  The reason is that USB-C uses DisplayPort for video natively (unless you use something like a USB-C to HDMI cable/adapter, which incorporates an active signal converter chip and will thus prevent daisy chaining).

If on the other hand your USB-C port does not support video output and you don't have a DisplayPort output, you can't set up a daisy chain.  Fyi when asking for technical assistance like this, it helps to provide basic system information such as the system model you're dealing with, even if it's a non-Dell system.

@jphughan Many thanks for clarifying.

My laptop is a Lenovo ideapad S340-15IIL, Model name 81VW.

I think you are also saying that HDMI cable does not support daisy chaining ie I could not connect the second U2715H via HDMI cable to the first U2715H (with the first connected to laptop via HDMI)?

I assume the USB-C port supports video as the laptop has a separate non USB-C power port. Maybe wishful thinking?

@nomoreusernames  Correct, you need to be using cables and connectors that run DisplayPort protocol along the entire chain.  There is a tiny exception to that rule for the LAST display in the chain.  Basically, if you connect an active DisplayPort to HDMI adapter to the DisplayPort output of the second-to-last display in the chain, you can use that to feed an HDMI input on the last display.  The reason this works is that in this case, the adapter itself is performing the conversion (as opposed to a passive DP to HDMI adapter that relies on the source falling back to native HDMI signaling), and since the last display doesn't need to continue the chain, it doesn't matter that the HDMI conversion is occurring at that spot.  But that's an edge case.

As for your laptop, Lenovo's PSREF spec sheet here only says that it's a "USB 3.1 Type-C Gen 1" port.  That to me indicates that it only supports USB 3.1 Gen 1 data, because if you look at the spec sheet of a system like the ThinkPad T490s here, you'll see that its specs specifically mention DisplayPort output support.

Unfortunately there's no way to run multiple independent displays from an HDMI output.  The signal protocol just doesn't support it; DisplayPort works in a fundamentally different way.