Same problem here. Dell support says it's not compatible with Thunderbolt!

According to the specifications page, it seems to have 2 Thunderbolt 4 ports.  The USB C on the other side does have a Display adapter option if you have one of those.

Unless it might be system specific, it appears as if Thunderbolt 4 should work.  I do not know what type of Device Manager devices it might show. 

I will check and see if one of my systems has it but the newer Processor/chipset combinations may cause it to look different.

If you install intel thunderbolt manager, you suppose to see Port one and Port two with connected device under each port. On my 9520 Intel TB manager don't show any port. In device manager, under system device, you need to see TB controller (I've included a screenshot from a lenovo)

. I also found that if I disabled TB in BIOS, nothing change under device manager, I can saw the same hardware. Dell Technician just change the TB controller and no result, it's seems to be software specific.  I will try to downgrade the bios.

The guy from support who answer that doesn't want to work. I can confirm that the MOTU wotk fine on a Lenovo Yoga, a Surface Pro 8 and an asus motherboard with TB4.  As all thunderbolt chipset are produced by Intel, the MOTU should work on any TB controller. The technician confirm that there's a problem with the laptop and  ask for an exchange.

My laptop is showing one Thunderbolt controller in Device Manager under System devices.  I only have one USB c port which is capable.

The 9520 also has a similar situation with the Wi-Fi card being 6e capable but not usable.  The spec page shows only Wi-Fi 6 so technically they never claimed it was 6e capable. 

But your system definitely shows TB4 capability.  Is the sound device the only TB device you have?

just found that in Thunderbolt control center, Lenovo on my desktop are show as TB4 device but XPS are show as USB4 device.

I've already try an Apollo twin X with same result. I just remember that you can connect 2 PC over Thunderbolt. I've connect my lenovo with my desktop with an anker TB4 cable and it's working, I can transfer files between  both pc. I've tried to connect the 9520 with the lenovo then with my desktop, nothing happens, the xps don't see other pc over TB. I've a wd22tb4. It's working with the XPS but if I look in device manager, all hardware I connect on the dock are show under USB4 and not TB. I know that the Dell dock work differently. Maximum PD on TB is 100w but Dell dock can deliver 130w.

What Firmware version is your XPS running?

I have the same issue, my xps 9520 is up to date with bios and drivers and my WD22TB4 is showing only under USB4 not TB4. I cannot have both of my 4k monitor at 60hz, only 60hz and 30hz, super annoying.

On my Asus Desktop, there is a setting in the Bios regarding tunneling USB4 through Thunderbolt.  I am not sure what that means but I don't have a Thunderbolt device to check.

You might just check your Bios to see if you have such a thing.