If it's handled correctly, his phone was put in a faraday bag on site and it won't be brought out until it's in a faraday cage. They're going to go through his phone with a fine toothed comb, after backing it up in the cage so it can't dial out or receive a remote killswitch. If they find anything, ANYTHING, on it that is illegal, they can take action.
Pictures of underaged people transitioning or asking for advice about genitals or top surgery. Him sending inappropriate texts, images, or communications to underage kids. Evidence of his narcotics trafficking.
The fact that they purged the discord highly suggests there was something in there that he didn't want law enforcement to see. Do you think he kept that purely on discord, or might he have saved some of that shit to his phone?