@amosbatto DisplayPort alt-mode is in fact how most USB-C to HDMI adapters work. HDMI alt-mode, although it exists, is rather rare and not supported that well across various hardware.
@dos, Oh I assumed that DP alt-mode was like normal DP, but I Googled it and found that there is no DP Dual Mode (DP++) over DP alt-mode, so it isn't possible to send an HDMI signal over DP alt-mode. We will need an active adapter to convert from DP to HDMI.
This article explains it:
@amosbatto Yes, I know, and I said that earlier - most USB-C to HDMI adapters use DP alt-mode, which is universally supported, and not HDMI alt-mode, which is rather rare and can't be used together with USB signal at the same time.
@dos, HDMI alt-mode not being common gives me hope for the future. As more devices move to USB-C, we can get rid of HDMI, which requires licensing fees, and just use DisplayPort, which is a freer standard. Nice to find something positive in this dreary world.