[bastawhiz]

It's relevant because the display just needs an HDMI port. You can plug a HDMI-to-USC-C cable into a computer and a TV or projector and it'll work using this. If your device doesn't do displayport then displayport support is moot.

[crote]

Virtually all USB-C-to-HDMI cables use DisplayPort Alt Mode and internally convert from DP to HDMI.

[lxgr]

Were there ever any (source) devices with HDMI alt mode shipped, though? I vaguely remember hearing about one smartphone, but that seemed more like a showcase for the technology.

[seba_dos1]

It's irrelevant. The linked page is several years old; HDMI alt-mode didn't catch on and virtually nothing implements it.