The minimum requirements for the Rift-S list a display port or mini display port as needed. https://www.oculus.com/rift-s/
Display Port (which has been around for 11 years) is actually the superior standard to HDMI. It's probably the most common port on PC graphics cards at the moment, many having 3 display ports and only 1 hdmi port.
It's also cheaper, HDMI requires manufacturers to pay royalties to HDMI Licensing LLC. Display Port is owned by VESA, who don't charge royalties.