Ah the port does work with a different device (Pixel 5 phone). It just doesn't work with my USB audio interface, which works fine with a USB-A/C adapter instead.
I am running linux with kernel 5.18 on my XPS 8950. The USB-C ports do not work; nothing plugged in is discovered. The kernel is also printing errors about this port occasionally:   Unfortunately I did not try the ports on Windows before installing Linux, so I can't rule out a hardware problem. Does anyone know a solution?
XPS 8950 USB-C ports not working on linux