Thanks for your answer, It's powered by the same power strip. Just a couple of hours after opening this post I got an Steam machine update and It seems to be fixed (omg what a coincidence), but I will keep testing and providing feedback to confirm that.

**Summary**
Intermittent audio crackling/cutouts occur when playing Factorio on a Linux (SteamOS) system outputting audio via HDMI to an AV receiver. The issue is present for roughly the first 15 minutes after launching the game and then stops occurring on its own, without any change in game context ...