The thing I found limiting when I tried to run Steam remotely from my lounge room was the need to actually interact with the host PC at certain points, not just during the initial setup. I found this is the same on a lot of similar platforms, and it’s made worse when RDP clobbers the graphics settings.

A truly headless solution with a web ui would get me really interested.

Valve has truly headless runner (gamescope) for Linux, e.g. you can start it manually from command-line over ssh

  gamescope \
    --backend headless \
    -W 1920 -H 1080 \
    -w 3840 -h 2160 \
    -r 60 \
    --cursor-scale-height 1080 \
    --force-grab-cursor \
    -- steam -gamepadui -pipewire-dmabuf

But it has many issues compared to Games on Whales, for example, which is much more efficient and scales cursor better.

https://github.com/ValveSoftware/gamescope

Furthermore, it will log in and unlock your host pc. If you're across town at a coffee shop and your 4 year old kids are near the host pc and see it unlock and start playing a game, you better believe they're gonna wreck your save file.

Not to mention greater security concerns.