I ask because Lutris was killing my network too and it took me like two weeks to figure out the root cause. For me, this is what was happening. I had Dead Space Remake installed. Lutris used the name of the game to identify it, but was incorrect. Then it would try to download assets for the game but apparently they changed the URL path. But when Lutris failed to get them, instead of giving up, it HAMMERED my DNS with requests, triggering pihole to engage its flood controls and kick me off DNS for 5 min.
If you use pihole, watch your query log live and see what is happening.
I am using pihole. I will take a look and see if that is happening and report back.
How did you end up fixing the issue?
EDIT: Checked in on it and this is indeed the issue. Heroic is generating thousands of requests and I assume phile is flood controlling it. Two questions:
How can I confirm pihole is flood controlling it? Found a message confirming the rate limiting under Tools -> Pi-hole diagnosis
First I disabled the flood control just to make sure I could get it working. I'm not sure about Heroic, but Lutris has an online database for games and I looked up Dead Space and found the correct game ID to set it to. Once it was on the right ID, it found the assets it needed and was done in under a second.
No problem, glad I was able to recognize the symptoms so quickly. It was incredibly frustrating too! Oh, one more thing to do is launch Heroic from terminal so you can see the output. That's how I knew which game was causing it.