With all due respect, I'm struggling to parse this part of your comment.

With that said, I'm pretty sure your target is calling this API method:

https://partner.steamgames.com/doc/api/steam_api#SteamAPI_Re...

If you don't care about being authenticated with a "legit" session for online play, just strip SteamStub and apply a Steam emu with the necessary config. Those will obviously not care about wherever they are being launched from. I recommend the CODEX one if your target is not too recent.