Inspired by this post on reddit, I wrote a simple bash-oneliner to check for availibility of a specific game/program on Steam.

Requirements:

1. wget, curl or an equal tool
2. the numerical appid for the game/program to check from steam
3. the JSON-tool jq (most likely included in your distro)

With these requirements fulfilled, you can check the linux-availibility from command-line like this:

wget http://store.steampowered.com/api/appdetails?appids=255220 -O - | jq '.[] | { name: .data.name , linux: .data.platforms.linux }'

Output:

{
"name": "GRID Autosport",
"linux": false
}

Replace 255220 with whatever your appid is.

You can extend this from here for all your needs, e.g. build a loop or check for more appids at once...